Mr. Ramos Genetics Study Guide

Students, here is a study guide for the Genetics Test. Read it and study it carefully in conjunction with your class & book notes. The Genetics test has 50 Multiple Choice questions worth 50% of your total class grade. The test is curved. Also, take advantage of this generous study guide. I will NOT always do these nice things for you all.

Cell GrowthSC.912.L.16.8 Explain the relationship between mutation, cell cycle, and uncontrolled cell growth potentially resulting in cancer.

Cell Cycle-Cells grow and divide. This is what we call the cell cycle.

-The cell cycle is divided in two parts called interphase and mitosis. -Interphase deals with growth, and mitosis deals with cell division.

-Interphase is further divided into 3 parts: G1, S, and G2

G1 = cell growsS = DNA is replicated (aka copied)G2 = more cell growth & organelle replication

Keep in mind that not all cells grow and divide. Neurons and muscle cells do not grow or divide. We refer to their special state as G0.

Liver cells are also in G0 just like neurons and muscles, but liver cells have the ability to re-enter the cell cycle and divide when they are needed.

Check-Points-Cells undergo check points throughout several stages of the cell cycle. If the cell does not pass the check-point, it is programmed to kill itself. -The cell suicide process is called apoptosis (this kind of suicide is good…otherwise you get cancer)

-Check-points prevent DNA errors that may have serious consequences on

individuals.Cancer-Cancer is uncontrolled cell growth that spreads to other parts of the body (metastasis).-If the cell’s DNA becomes damaged and changed, we say that there is a DNA mutation. -These mutations, or genetic mistakes, begin to accumulate. If the problem is not solved, the cells may become cancerous.

-These mutations may cause cells to grow uncontrollably, disregarding check-points and the apoptotic (cell suicide) process. -As cells continue to grow and divide, they begin to clump up and form masses of cells called tumors.

-If the cells within the tumor stay in place and do not spread to other parts of the body, the tumor is called a benign tumor. Benign tumors are not cancerous.

- If the cells within the tumor spread to other parts of the body, the tumor is said to be malignant (evil). Malignant tumors are cancerous. -Fun fact: a fancy word for “spread” is “metastasis.” Malignant tumors have the ability to metastasize to other parts of the body.

Fun fact: watch out for the suffix “-oma,” which is indicative of a tumor (examples: carcinoma, melanoma, sarcoma, glioma, etc)

Cancer TreatmentSurgery is used if the tumor is localized and easy to remove (benign tumors). Sometimes doctors avoid surgery, because there is a risk that this may cause the cancer cells to spread during the operation.

Radiation therapy uses high energy radiation to kill cancer cells. Sometimes a laser beam is fired directly at a tumor to kill or shrink cancerous cells.

Chemotherapy involves injecting patients intravenously with chemicals that target cells in the body that multiply quickly. Since cancer cells multiply quickly, they will most likely die. Keep in mind that hair cells also multiply quickly, so they will die too. This is why people’s hair fall off during chemotherapy.

MitosisSC.912.L.16.14 Describe the cell cycle, including the process of mitosis. Explain the role of mitosis in the formation of new cells and its importance in maintaining chromosome number during asexual reproduction.SC.912.L.16.15: Compare and contrast binary fission and mitotic cell division.

MitosisMitosis is nuclear division, by definition; however, most people think of mitosis as cell division.

-The goal of mitosis is to produce two identical daughter cells. -Mitosis produces diploid cells.-Mitosis only produces somatic cells (body cells). It does NOT produce gametes (sex cells).

-Mitosis can be divided into 4 phases: prophase, metaphase, anaphase, and telophase. These stages occur continuously, but we separate them into phases to identify them during a test and to better explain what is occurring. *Remember PMAT.

In prophase, the DNA prepares itself for the mitotic journey by coiling up into chromosomes. The centrosomes begin to move to opposite poles of the cells.*Remember that when you move to a new home, you pack things into boxes sothat nothing gets lost & so it is easier for you to carry. The cells do the same thing. They pack their messy DNA into organized chromosomes.

In metaphase, the sister chromatids meet in the middle of the cell. The nucleus is no longer present at this point and the Centrosomes are on opposite ends of the cell

In anaphase, the sister chromatids are torn apart. They Centrosomes release spindle fibers that pull the chromatids apart and to opposite poles of the cell.

In telophase, everything comes back together. The nucleus and nucleolus re-forms, and the chromosomes become loose DNA again. At this point the two daughter cells are about to split in half.During Telophase of mitosis, cytokinesis occurs. Cytokinesis is the process by which the cell’s cytoplasm splits and two identical daughter cells are formed.

In animal cells, a cleavage furrow is formed during cytokinesis. This cleavage will eventually cause the two cells to split and become two independent cells.

In plant cells, a cell plate forms between the two plant cells. This cell plate eventually becomes the cell wall. Notice how the plant cells are stuck to each other.

Importance of MitosisMitosis is important because it allows somatic cells to regenerate. Somatic means body, so all cells in your body are somatic, with the exception of sperm and egg cells, which are called sex cells.

Human somatic cells contain 46 chromosomes. In order to create two identical cells, these 46 chromosomes must duplicate during the S-phase of Interphase to become 92 chromosomes. Then, the cell can divide in half so that each new cell acquires 46 chromosomes.

It is important to maintain the chromosome number. If the chromosome number changes, some disease or abnormality may result. In humans, the chromosome number is 46. Therefore, all somatic cells MUST have 46 chromosomes.

46

Chromosomes

S – phase (Interphase)

92

Chromosomes

46

Chromosomes

46

Chromosomes

Mitosis

Parent Cell

Daughter Cells

Parent Cell

Binary Fission vs. Mitosis-Remember that mitosis by definition is nuclear division. Bacteria, however, do not have nuclei. Therefore, bacteria do not undergo mitosis.

-Bacteria replicate through a process called binary fission (literally: to cut in half).During binary fission, bacteria replicate their circular DNA, send them to opposite poles of the cell, and the bacteria cut themselves in half.

-There is no prophase, metaphase, anaphase, or telophase in binary fission because these are phases of mitosis.

MeiosisSC.912.L.16.16 Describe the process of meiosis, including independent assortment and crossing over. Explain how reduction division results in the formation of haploid gametes or spores.

Meiosis-Meiosis produces 4 non-identical sex cells known as gametes. -Meiosis occurs in two divisions, which are called Meiosis I and Meiosis II.-Meiosis produces haploid cells.

-In males, meiosis only occurs in the testes to produce sperm cells. The sperm cell is the male gamete. -In females, meiosis only occurs in the ovaries to produce egg cells. The egg cell or ovum is the female gamete.

*Before we continue into meiosis, it is important to understand some chromosome terminology.Human Chromosomes are pieces of linear DNA that have been wrapped and condensed to make the process of cell division occur smoothly without losing any information.

Remember that humans have a total of 46 chromosomes (23 from dad and 23 from mom). At the end of meiosis, each sperm or egg cell will be left with only 23 chromosomes.

When DNA undergoes the S-phase of Interphase, the 46 human chromosomes make exact copies that result in 92 chromosomes. Each identical copy of the chromosome is called a sister chromatid. The sister chromatids will be joined together like Siamese twins at a center location called the centromere.

Moreover, for every chromosome you receive from your mom, you will receive a similar chromosome from your dad. These similar chromosomes are called homologous chromosomes.

At the end of mitosis or meiosis, the sister chromatids split to become an individual chromatid or chromosome.Meiosis I-Meiosis I is divided into prophase I, metaphase I, anaphase I, and telophase I.-2 non-identical daughter cells will be produced in meiosis I.

Prophase I is probably the most important and complicated phase of meiosis I. It is highly tested on exams. In prophase I, a mom chromosome will pair with a dad chromosome. The pairing only occurs for homologous chromosomes, which are those chromosomes from mom and dad that are similar (same size, same genes, etc). The pairing of these homologous chromosomes is called synapsis. Furthermore, because you can see a total of 4 sister chromatids in this homologous pairing, we call them tetrads.

Now, the most important thing will take happen. A piece of the mom chromosome will flip with a piece of the dad chromosome. They exchange genetic information. As a result, this is one reason why everyone on this planet looks different. Imagine all the combination of genes that take place during this random crossing over of genetic information.

In Metaphase I, the homologous chromosomes align themselves randomly in the middle of the cell, known as the metaphase plate. They will then be randomly separated during anaphase. This random separation of chromosomes and genes is known as independent assortment, and it is the second reason why everyone in the world is different. *Pay attention to this. In metaphase I, the tetrads align in the middle, while in metaphase II the sister chromatids align in the middle.

In anaphase I, the homologous chromosomes, or tetrads, are randomly pulled apart to opposite poles of the cell. *Pay attention to this. In anaphase I, the tetrads are separated, while in anaphase II the sister chromatids are separated.

In Telophase I and cytokinesis, two daughter cells are produced. Each daughter cell has now 46 chromosomes (instead of 92), and they will each undergo a second division in meiosis II to produce a total of 4 daughter cells with 23 chromosomes each.

Meiosis II-Meiosis II is divided into prophase II, metaphase II, anaphase II, and telophase II. -A total of 4 non-identical cells will be seen at the end of meiosis II.

Prophase II is not as interesting as prophase I. Prophase II is actually quite simple and boring. The only thing that happens in prophase II is that the nucleus breaks down and the DNA becomes chromosomes.

In metaphase II, the sister chromatids align in the metaphase plate. *Remember that in metaphase I the tetrads, or homologous chromosomes, aligned in the middle.

In anaphase II, the sister chromatids are pulled to opposite poles of the cell.*Remember that in anaphase I the tetrads, or homologous chromosomes, were pulled apart.

In Telophase II and cytokinesis, these two non-identical daughter cells split to become 4 non-identical daughter cells with 23 chromosomes each. These are called sex cells, or gametes. *Remember that in Telophase I we produced 2 non-identical daughter cells with46 chromosomes each.

Mitosis vs. MeiosisSC.912.L.16.17 Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation.

Comparison Graph

Mitosis Meiosis# of cells produced 2 4

Takes place Everywhere except testes & ovaries Testes and OvariesDiploid vs. Haploid Diploid Haploid

Reproduction Asexual SexualChromosome Count 46 23

# of divisions 1 2Type of cell produced Somatic cells (body cells) Sex cells (gametes)

Examples of cells Skin cells, hair cells, liver cells, etc Sperm and egg cells only

-A diploid cell contains both sets of chromosomes. One set is from mom and the other set is from dad. The human diploid count is 46.

-A haploid cell contains half the set of chromosomes. The human haploid count is 23. Sperm and egg are haploid cells because they each contain 23 chromosomes.

Human Karyotype-A human karyotype is a picture taken of the human chromosomes to determine the sex: male or female.-The homologous chromosomes are paired and placed in order from longest to shortest.

- To determine the sex, look at the very last pair of chromosomes (pair #23). If you see two chromosomes that are the same size, then we refer to the sex as female. If you notice that one chromosome on the 23rd pair is much longer than the other one, we refer to the sex as male.- The female’s 23rd pair is XX, while the male is XY.

Many genetic disorders occur on the X chromosome. These diseases that affect the sex chromosomes are known as sex-linked diseases.

Fortunately for females, they are usually not affected by these sex-linked diseases because they have a back-up X chromosome in case one fails. Remember women are XX.

Unfortunately for males, they are more prone to suffer from sex-linked diseases since they only have one X chromosome and one Y. If the X chromosome is damaged, then genetic

diseases, such as Hemophilia, ALD, color blindness, and more are seen in males. These diseases may also occur in females, but are less common.

Reproductive SystemsSC.912.L.16.13 Describe the basic anatomy and physiology of the human reproductive system. Describe the process of human development from fertilization to birth and major changes that occur in each trimester of pregnancy.

Purpose of Reproduction-The purpose of reproduction is to populate the world and to pass on one’s genetic information to the next generation. - Sexual reproduction leads to genetic variation.

-The main function of the male reproductive system is to make sperm cells.-The main function of the female reproductive system is to make egg cells, or ova.

Male Reproductive SystemThe journey of sperm cells: 1. Sperm cells are made in the testes. (The male hormone testosterone is also produced in the testes)2. Sperm cells travel to the epididymis to grow and mature.3. Sperm cells then travel up and around the vas deferens.4. The vas deferens becomes the urethra and the sperm is bathed in a milky fluid known as seminal fluid.5. The prostate gland and seminal vesicle release the seminal fluid onto the sperm cells. This combination of sperm and fluid is called semen. 6. The semen continues to travel down the urethra until it is released from the penis.

*It is important to note that the bladder, an organ that contains urine, is not part of the reproductive system. It is actually part of the urinary system. Both, urine and semen travel through the urethra and out of the penis.

The testes are located outside of the body in a sac called the scrotum. Sperm cells die when it gets too hot, so the testes are outside the body where it tends to be a bit cooler for sperm cells to survive.

Female Reproductive SystemThe journey of egg cells:1. Egg cells are made in the ovaries. (The female hormone Estrogen is also made in the ovaries)2. Usually one egg cell is released every month from one of the ovaries. This process is called ovulation.3. The egg cell will travel down the entire length of the fallopian tube (some books refer to the fallopian tube as the oviduct or uterine tube)4. The egg cell must be fertilized by a sperm cell while it is in the fallopian tube. If fertilization does not take place during this time, the egg cell will die. This is a common test question: Where does fertilization occur? In the fallopian tube5. If the egg cell is fertilized, it will ultimately become a blastocyst. The blastocyst will implant itself on the wall of the uterus to become an embryo and then a fetus. 6. After about 9 months, the fetus is ready to be delivered. The cervix, which is the neck of the uterus, will dilate so the fetus can move into the vagina, or birth canal. 7. The fetus then exits the female’s body through the vagina, or birth canal.

*It is important to note that babies DO NOT grow in the stomach!! Otherwise you would have a barbecued baby. The baby grows and develops in the uterus.

DNA and RNA

Introduction to DNA and RNA-DNA stands for deoxyribonucleic acid. -RNA stands for ribonucleic acid.-All nucleic acids (DNA and RNA) are composed of basic building blocks called nucleotides.

-DNA is double stranded (double helix/twisted ladder).-RNA is single stranded.

-A nucleotide is composed of a sugar, a phosphate, and a nitrogenous base. -The sugar in DNA is called deoxyribose. -The sugar in RNA is called ribose.

-DNA contains 4 nitrogenous bases: A, T, C, G-RNA contains 4 nitrogenous bases : A, U, C, G

Uterus

Stomach

Nucleotide

Notice above that DNA and RNA share the bases A, C, and G. However, the base “T” is only found in DNA while the base “U” is only found in RNA.

Nitrogenous basesA = adenineG = guanineC = cytosine U = uracilT = thymine

-The purines are adenine and guanine. These are bases that have two rings. -The pyrimidines are cytosine, uracil, and thymine. These bases have one ring. *Mnemonic: pyramids cut. (Pyrimadines: cytosine, uracil, thymine)

-Purines will always attach themselves to pyrimidines. - Adenine will always pair with thymine in DNA. A double hydrogen bond holds them together.-Guanine will always pair with cytosine in DNA. A triple hydrogen bond holds them together.

In RNA, adenine will pair with uracil, since there is no thymine in RNA.

*So what is the difference between deoxyribose and ribose? Take a look belowDeoxyribose literally means, “a ribose without oxygen.”

Comparing DNA and RNA

Purine

Pyrimidine

Nucleic Acid DNA RNASugar Deoxyribose RiboseBases A, T, C, G A, U, C, GStrands 2 strands 1 strand

The structure of DNA is anti-parallel. Notice above (picture on the right) that the pointy tip of the DNA pentagon is pointing up on the left DNA strand, but on the right strand the pointy tip of the pentagon is pointing down.

*Important: the sugars and phosphates make up the backbone of the DNA ladder, while the bases make up the rungs (aka steps) of the ladder.

DNA HistoryBritish scientist Rosalind Franklin took an X-ray picture of DNA in 1952.

(X-ray Crystallography)

American biologist James Watson and British physicist Francis Crick used the X-ray picture from Rosalind Franklin to finish their 3-dimensional model of DNA. Watson and Crick later received the Nobel Prize, while Rosalind Franklin died and never won anything.

DNA ReplicationSC.912.L.16.3

Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic information.

SC.912.L.15.15 Describe how mutation and genetic recombination increase genetic variation.

SC.912.L.16.4Explain how mutations in the DNA sequence may or may not result in phenotypic change. Explain how mutations in gametes may result in phenotypic changes in offspring.

Introduction to DNA ReplicationCells must replicate their DNA before they divide. This occurs in the S-phase of Interphase.

DNA strands are complementary. This means that if you know one strand of DNA, you can draw its second strand.

DNA strand: 3’– A T T A G C T C – 5’DNA strand: 5’ – T A A T C G A G – 3’ *Notice that the strands are also anti-parallel. The 3’-end is complementary to the 5’-end.

DNA replication is semi-conservative. This means that when DNA replicates, it will contain one old strand and one new strand.

The Process of DNA Replication1. The enzyme helicase unwinds the double stranded DNA.

2. Single-Strand Binding Proteins (SSBs) attach to the DNA strands to prevent reannealing.

3. Primse adds RNA primers to both strands of DNA.

Complementary Strands

SSBs

4. DNA polymerase searches for the RNA primers that were created by primase. DNA polymerase then adds DNA nucleotides in a 5’ 3’ direction. Because DNA polymerase can only add nucleotides in a 5’ 3’ direction, one strand will grow continously (leading strand) while the other strand will have to be made in discontinously (lagging strand) in fragments called Okazaki fragments.

5. The pieces of RNA must be removed from DNA. RNase H will remove the RNA primers from the DNA.

6. Another DNA polymerase returns and fills in the Okazaki fragments from the removal of the RNA primers.

Leading Strand

Lagging Strand

RNase H DNA polymerase

RNA primer

7. Finally, Ligase must link short strands of DNA. This completes the process of DNA replication.

Mutations in DNAIf I asked you to copy a book by hand, what are the chances that you will not make a mistake during the copying process? Do think you can copy a book with extreme precision and detail, such that you will not miss a comma, capital letter, or period?

The enzymes in charge of DNA replication sometimes make mistakes when they copy DNA. These mistakes are called mutations.

Just one tiny mistake may ruin your life. Look below how one tiny change in a DNA base causes an individual to develop a disease of the blood called sickle-cell anemia. That one tiny change caused the amino acid valine to form instead of glutamic acid. The mutation shown below is an example of a point mutation.

*Relax, although a lot of mutations are occuring in your body every single day, not all of them are dangerous. In order for your future child to inherit one of these diseases, the mutation must occur in the sex cells (sperm and egg) during meiosis.

Types of Mutations-As you saw in the picture above, sickle-cell anemia is an example of a point mutation. -There are three types of point mutations: silent mutation, missense mutation, and nonsense mutation.

Point Mutations:1. Silent mutation: This is a point mutation that does not change the amino acid sequence in the protein. It is silent because nothing really happens.2. Missense mutation: This point mutation creates a brand new amino acid sequence in the protein. Sickle cell anemia is an example of a missense point mutation. 3. Nonsense mutation: This point mutation does not code for any amino acid. It causes the amino acid chain to stop.

*Notice in the picture above how the normal amino acid should be lysine (Lys). With a silent mutation, the same amino acid (Lys) is still made even though there was a change in the DNA. With a nonsense mutation, no amino acid is placed and the protein STOPS. Finally, with the missense mutation, a different amino acid results.

The most dangerous types of mutations are those that cause the DNA frame to shift. These are called frameshift mutations. Any addition or deletion of a base may cause the DNA frame to shift. Therefore, additions and deletions may lead to frameshift mutations.

Point mutations are base-substitution mutations; they are NOT frameshift mutations.

Notice the picture to the right. The deletion of the base “G” from “GAA” causes a shift in the entire DNA sequence. This shift now contains the new DNA information “AGG,” “CAC,” and “GT,” which will now create the amino acids Lys and His, instead of the normal code of Glu, Ala, and Gly.

This is how a frameshift mutation looks like in an english sentence.Normal: THE CAT AND THE MAN ARE FATDeletion of “T” in “THE”: HEC ATA NDT HEM ANA REF ATInsertion of “A” (random letter): ATH ECA TAN DTH EMA NAR EFA TDo you see why frameshift mutations are so bad!?

Protein SynthesisSC.912.L.16.5 Explain the basic processes of transcription and translation, and how they result in the expression of genes.SC.912.L.16.9Explain how and why the genetic code is universal and is common to almost all organisms.

Introduction to Protein SynthesisCells carry out life functions by making proteins. Everything in your body is protein with some exceptions, such as your skeleton and teeth.

Central Dogma of Molecular Biology: DNA RNA Protein

Image all of us in a cooking school. DNA is our cook book and the chefs are called ribosomes.. It contains all the recipes to make different kinds of foods, or proteins. (Ribosomes make proteins)

If we have 1 cook book called DNA, and we have 30 chefs, we need to do something so that each chef has a copy of the recipe they are going to cook. Therefore, we make plenty of photocopies of the recipe, which we call RNA.

There are 3 common types of RNA: mRNA, rRNA, and tRNA.

The photocopies that we just made with our “recipe” is called mRNA (messenger RNA) because it carries the message, or the recipe. In eukaryotes, this message (mRNA) is carried out of the nucleus into the cytoplasm.

The chefs, or ribosomes, need to grab that message (mRNA). The ribosome will read the message and try to make a protein. Unfortunately, the ribosome doesn’t have any supplies to cook this recipe, so a tRNA (transfer RNA) must transfer those supplies to the ribosome. Each tRNA will transfer 1 amino acid to the ribosome. Remember that lots of amino acids add up to make a protein.

rRNA or ribosomal RNA is simply the RNA found within the ribosome. There is nothing special about this kind of RNA. Think of it as the “uniform of the chef.”

When DNA is turned into RNA, the process is called transcription.When RNA is turned into protein, the process is called translation.

TranscriptionIn eukaryotes, transcription takes place in the nucleus of the cell. In transcription, the DNA will be “photocopied” or “transcribed” into RNA (specifically mRNA).

*It is extremely important for the test that you know how to transcribe a piece of RNA from DNA. I will provide you with a piece of DNA, and I am going to show you how to transcribe it. Look belowDNA strand: 3’– A T T A G C T C – 5’DNA strand: 5’ – T A A T C G A G – 3’ (let’s use this DNA strand to create our mRNA template) mRNA: 3’ – A U U A G C U C – 5’ (Notice how we use “U” in RNA instead of “T”)

Finally, the mRNA that we just created needs to be edited. To finalize our mRNA, we need to remove a piece of the mRNA called the intron. Remove all the introns. We are now done with transcription.

TranslationTranslation is the process by which RNA is translated to protein, and it occurs in the cytoplasm for both eukaryotes and prokaryotes.

In translation, a ribosome grabs on to the mRNA and begins to read its message. Several tRNA, each carrying one amino acid, will head toward the ribosome. The ribosome will grab on to the tRNA based on the instructions from the mRNA.

The mRNA is read 3 letters at a time. These three letters is called a codon. The first three letters, or first codon, in all proteins is the start codon AUG. AUG codes for the amino acid methionine.

The ribosome must attach a tRNA with the anti-codon UAC to the codon AUG on the mRNA. Look at the picture to the right

Once the tRNA leaves its amino acid, the tRNA is discarded, or thrown away. Remember, every tRNA brings only 1 amino acid.

*On the exam, I will give you an mRNA strand and ask you to place the right amino acids according to the strand. For example, notice the RNA picture above. GUG codes for Val. CAC codes for His. CUG codes for Leu. Every three letters (codon) codes for 1 amino acid.

Use this chart to create your protein. Every three letters is one amino acid.

mRNA: AUG – UAU – CGU – GUU – CUA – GGU – UAAProtein: Met – Tyr – Arg – Val – Leu – Gly – Stop

You do not need to memorize the names of the amino acids. You do not need to memorize that Met stands for methionine, or Tyr stands for tyrosine, etc…

Mendelian GeneticsSC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.SC.912.L.16.2 Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.SC.912.L.14.6 Explain the significance of genetic factors, environmental factors, and pathogenic agents to health from the perspectives of both individual and public health.

Introduction to HeredityGregor Mendel is the father of heredity. He did hundreds of experiments on pea plants. Unfortunately, he was not recognized for his work until years after his death.

*Before we continue, let us go over the concept of a gene and an allele.Let’s say we want to study eye color. Let “B” represent brown eyes and “b” represent blue eyes. Remember that you have two parents (a mommy and a daddy), so you will get one letter from each parent. You have three different mathematical possibilites: BB or Bb or bb

I have to memorize every amino acid and every 3 letter code????

Eh, relax doc. You don’t.

I will give you a chart.

If you get BB, then you have brown eyes. If you get bb, then you have blue eyes. But what if you get Bb? Does this mean you have one brown and one blue eye? Absolutely NOT. If you get Bb, then you have brown eyes. (I will explain why in a moment)

The two letters combined “BB”, “Bb”, and “bb” represent genes. Genes are segments of DNA that code for a specific protein.

Each individual letter “B” or “b” is called an allele. Therefore, your mom gives you one allele and your dad gives you the other allele.

BB= Gene Bb = Gene bb= Gene B = allele b =allele

Mendel’s Laws

1. Law of Dominance: The dominant allele will be expressed. * Remember Bb = brown eyes. This occurs because brown is dominant to blue, so brown is physically expressed while blue is hidden.

2. Law of Segregation: In meiosis (back when sperms and eggs were made), the alleles were segregated, or separated. As a result, every sperm and egg is different. Then, each time a baby is formed, the baby looks slightly different from his or her mom, dad, brother, sister, etc…

3. Law of Independent Assortment: Independent traits, such as eye color and hair color, assort themselves indepdently. In other words, just because you have blue eyes does not mean you will automatically have blue hair.

How did Mendel figure this out? 1. Gregor Mendel got a purple pea plant and self-fertilized it to create a pure breed (PP = purple).2. Gregor Mendel got a white pea plant and self-fertilized it to create a pure breed (pp = white)

*Notice how we use “P” for purple and “p” for white. We keep the letters the same, but one letter is big and one is small.

3. Gregor Mendel then did an experiment. He got his pure purple pea plant and crossed fertilized it with his pure white flower. To his surprise, 100% of the pea plants were purple! What happened to the white!? Did it dissapear?

4. Mendel then got one purple pea plant that was produced from the purple and white parent pea plants. He calls these purple pea plants the F1 Generation because they are the offspring of the parent generation above.

5. When Mendel self-fertilized a purple pea plant from the F1 generation, he got the following results: 75% purple and 25% white pea plants. The white did not dissapear! It reappeared in this new generation, which he called the F2 generation.

The Punnett Square (Monohybrid Cross)

Scientists today use punnett squares to predict outcomes. A punnet square is a box (literally a square) that we will used to determine probabilities.

Let’s use the following assumptions to create a punnet square:

Example 1:1. Assume your mom has brown eyes and has the genotype BB. (the genotype, or genes are the two letters)2. Assume your dad has blue eyes and has the genotype bb.3. Let’s create a punnett square to determine the probabilities that you or your siblings will come out with brown or blue eyes.

If you notice from the punnett square above, all of the children of mom and dad have the genotype “Bb.” This means that they all have brown eyes, since brown is dominant over blue. However since they have a little “b,” they have the possibility of passing that “b” allele to the next generation.

Example 2:1. Assume your mom has brown eyes and has the genotype Bb.2. Assume your dad has brown eyes and has the genotype Bb.3. Let’s create a punnett square to determine the probabilities that you or your siblings will come out with brown or blue eyes.

b b

B B

B b

B b

Bb Bb

Bb Bb

BB Bb

Bb bb

Notice how ¾, or 75%, of the children will have brown eyes. Notice how ¼ of the children, or 25%, will have blue eyes.

*Since we are only studying one gene in this punnett square (eye color), we call this a monohybrid cross.

Genotype vs. Phenotype

As stated above, a genotype is the gene, or genetic make-up, of an organism. In the examples above, the three genotypes for eye color were “BB”, “Bb”, and “bb.” These genotypes were used to describe brown and blue eyes color.

Phenotype is the physical manifestation of an organisms genotype. For example, the physical manifestation of an organism with the genotype “BB” is brown eyes. Therefore, brown is the phenotype. The physical manifestation of an organism with the genotype “bb” is blue eyes. Therefore, blue is the phenotype.

Try this:1. Look at your eyes in the mirror and tell me your genotype…………you can’t!2. Now, look at your eyes in the mirror and tell me your phenotype…..do you have blue, brown green, etc?

As you probably inferred, you can tell a person’s phenotype by simply looking at them, but you cannot determine their genotype by simply looking at them.

Homozygous and Heterozygous Genotypes

The genotype BB is homozygous dominant. (Also known as purebred)

The genotype bb is homozygous recessive. (Also known as purebred)

The genotype Bb is heterozygous. (Also known as hybrid)

*This is extremely important for the test. The math problems that you will solve on the test will use these fancy words.

Test Example Question:1. Alberto and Jennifer are thinking of having children and would like to know the probabilitie of having a child with brown or blue eyes. Alberto has brown eyes and Jennifer has blue eyes. They go see a geneticist to discuss these possibilities. The genetecist informs Alberto that he is heterozygous while

Jennifer is homozygous recessive. Figure out the possibilites that their children will have brown or blue eyes by creating a punnett square.

2. Since Alberto has brown eyes, his genotype is either BB or Bb. If you continue reading, it says that Alberto is heterozygous. This means that he must be Bb.

3. Jennifer has blue eyes. The passage above states that Jennifer is homozygous recessive. Jennifer must then have the genotype bb. Even if the passage would not have said that Jennifer was homozygous recessive, we still know that the genotype is bb because there is only one genotype for blue eyes, since it is a recessive trait.

4. Create a punnett square and solve

Notice that 2/4, or 50%, of the children will have brown eyes, and 2/4, or 50%, of the children will have blue eyes.

The Punnett Square (dihybrid Cross)

Sometimes we want to study two traits at the same time. In this example, the two traits we will study are shape and color of seeds.

In terms of shape, round is dominant to wrinkled.R = round r = wrinkled

In terms of color, yellow is dominant to green. Y = yellow y = green

In this example we are going to make the following cross between two plants: RrYy x RrYyRemember that “R & r” represent shape and “Y & y” represent color.

b b

B b

BB bb

Bb bb

The first plant’s genotype is RrYy, so this plant has round seeds and yellow color. The second plant’s genoptype is identical to the first plant. To solve this problem, we need to make a bigger punnett square with 16 boxes, but how?

Let’s use a concept from math called FOIL: RrYy RY Ry rY ry(both plants in this example have the same genotype)

Test CrossA test cross is a test used to determine if a dominant individual is homozygous or heterozygous.

Let’s use the example of widow’s peak, which is a dominant trait. If an individual has a widow’s peak, he or she may be WW or Ww. So if you look at the picture to the right, is Eddie from “The Munsters” homozygous (WW) or heterozygous (Ww)? You don’t really know.

So the question is, how do we determine if Eddie Munster is homozygous (WW) or heterozygous (Ww). The answer is, we need to have him marry and mate with a female who does not have a widow’s peak (ww).

Let’s use Elena from “The Vampire Diaries” since she does not have a widow’s peak and is therefore homozygous recessive (ww).

*Keep in mind that this is a probability, or a chance event. -If all of the children have a widow’s peak, then Eddie Munster is more than likely WW. -If at least one of the children does NOT have a widow’s peak, then Eddie Munster is Ww. - If you are in doubt, do a punnett square and you will see.

Single-Gene Traits and Polygenic-geneTraitsWhat do the following four features below have in common? They are all single-gene traits, which means that they are all affected by only one gene. Single-gene traits are easy because you either have them or you don’t. This allows us to create punnett squares. Single-gene traits can also determine if a person is adopted or not.

On the other hand, polygenic-gene traits, are affected by two or more genes. Therefore, they are much harder to be used to determine important information like whether someone is adopted or not.

Beyond Mendelian Genetics: Incomplete Dominance, Codominance, & Sex-Linked Traits

Some traits do not follow the laws that we learned from Gregor Mendel, especially the law of dominance.

Incomplete dominance occurs when neither trait is dominant over the other. A blend of the traits appears.

Codominance is when both alleles are expressed. Look at the Dalmatian to the right. The Dalmation is NOT a blend of white and black. The Dalmation IS both white and black.

The examples that will be used on test for codominance are based on blood types, so learn this.

For codominant traits we use superscripts:Blood Type A: IAIA or IAiBlood Type B: IBIB or IBiBlood Type AB: IAIB (blood type AB is the only blood type that is codominant)Blood Type O: ii (notice that O-blood is recessive, and we use ii)

Blood types can also be used to determine if a person is adopted or not. Read at the example below.

The Charlie Chaplin case: In 1941, Charlie Chaplin became romantically involved with a young actress named Joan Barry. In 1943, twenty months after the relationship ended, she had a child and claimed Charlie Chaplin as the father. A paternity suit ensued. Chaplin had type O blood. Barry had type A blood. The baby had type B blood. Was the baby Chaplin’s? (Yes or No) Provide written explanation and/or charts to support your answer.

Blood Genotype: ii Blood Genotype: I AIA or IAi

Draw a Punnett square and find out if Chaplin really is the baby’s daddy. Since Chaplin has blood type O, which is recessive, use the alleles ii. Since Joan Barry is blood type A, she may have the genotype IAIA or IAi. On the other hand, the baby is blood type B, which means that the baby’s genotype must be IBi, it cannot be IBIB because we know the mother, Joan Barry, does not carry “B” alleles.

The conclusion:The baby could not have been Chaplin’s, since the B allele carried from the baby did not come from its mother and could not have come from Chaplin either. Three pathologists testified to this effect. However, the jury was undeterred by the “scientific evidence” and ruled that Chaplin was the father, ordering him to pay child support.

That’s not my baby!

You are still going to pay

child support! LOSER =P

Sex-Linked TraitsSex-linked traits are traits that are passed down to the child by the sex chromosomes (XX or XY).

Most sex-linked traits are carried on the X chromosome and most are recessive traits. This means that for a female to have the disease, she would need two defective X chromosomes. The male, however, only needs one defective X chromosome to inherit the condition.

Hemophilia is a blood-clotting disorder carried on the X chromosome. It is referred to as an X-linked recessive trait, since a female needs two defective X chromosomes to inherit the disease.

Look at the example to the right, the mother is a carrier for hemophilia, which means that she does not have the disease (XXh). The father does have hemophilia since his only X chromosome is defective (XhY).

PedigreesHE.912.C.1.4 Analyze how heredity and family history can impact personal health.

A pedigree is a picture representation of a family history. Pedigrees help us determine the genotype of an organism.

Use the key below to understand how a pedigree works.

Autosomal Dominant Trait Characteristics:

1. Does not skip generation2. Appears in both sexes with equal frequency3. Both sexes can transmit the trait to the offspring4. Affected persons have at least one affected parent

Autosomal Recessive Trait Characteristics:

1. Skips generations2. Appears with equal frequency in both sexes3. Affected offspring are usually born to unaffected parents. 4. Appears more frequent in children of consanguine marriages

X-Linked Recessive Trait Characteristics: (Highly tested on exams)

1. Appears more often in males2. Not passed from father to son3. Passed from mother to son

4. Women may have the disease, but the majority of women are carriers5. Hemophilia & color blindness are examples

X-Linked Dominant Trait Characteristics:1. Appears in males and females, but they often appear more in females. In fact, all females of affected parents will have it.2. Does not skip generation3. Affected men pass the trait to all their daughters but not their sons4. Affected women (if heterozygous) pass the trait on to about ½ of their sons and daughters.

Y-Linked Trait Characteristics: (Extremely unlikely to be tested on exams)

1. Only men have it2. Trait is passed from father to son3. Do not skip generations4.Extremely rare

BiotechnologySC.912.L.16.12: Describe how basic DNA technology (restriction digestion by endonucleases, gel electrophoresis, polymerase chain reaction, ligation, and transformation) is used to construct recombinant DNA molecules (DNA cloning).SC.912.L.16.10 Evaluate the impact of biotechnology on the individual, society and the environment, including medical and ethical issues.

Introduction to BiotechnologyBiotechnology is the manipulation of living organisms or their parts to produce useful products.

With biotechnology, we can do the following things and much more?1. Paternity testing2. Cloning of organisms3. Crime investigation (Fingerprints/DNA analysis)4. Genetically modifying fruits and vegetables to produce larger amounts of foods that are also resistant to pests5. Using bacteria to produce human hormones, like insulin, to treat diabetes 6. Finding of the cure of hundreds of diseases in the future like diabetes, cancer, and HIV7. Being able to modify a human genetically (imagine instead of plastic surgery, genetic surgery; being able to change your eye color from brown to blue)

Gel electrophoresis

-Gel electrophoresis is a technique that separes DNA, RNA, or proteins fragments according to their size.

- Gel electrophoresis is commonly used in crime scenes to analyze the evidence with the suspects’s DNA. This procedure may also be used to determine paternity.

For the test, you need to be able to read a gel electrophoresis.

Cloning

Cloning is the artificial production of a cell or organism that is genetically identical to the parent cell or organism.

Dolly: First cloned animal in the year 1996

Gel electrophoresis is very simple to read.

Compare the “Evidence” with all four suspects shown on the picture to the left.

Notice that the “Evidence” matches with “Suspect 3”

This indicates that “Suspect 3” is probably guilty.

Follow the steps in the picture on the right

Recombinant DNA

Recombinant DNA is literally combining DNA from different organisms.

Combining DNA is done in a field of science called genetic engineering.

Viruses are used as vectors to insert the new DNA.

The hormone insulin is now made with the help of bacteria. Therefore, we are able to manufacture insulin very efficiently and at a low cost. (Highly tested on exams)

Restriction enzymes are like scissors. In this example, we use a restriction enzyme to cut out the gene that codes for insulin in humans. We then combine that human gene with a bacterial circular chromosome called a plasmid. The plasmid is then inserted in the bacterium. The bacterium is now capable of producing human insulin.

In addition, we can use a technique called polymerase chain reaction (PCR) to make hundreds of copies of the gene, in this case the insulin gene. These copies can then be transferred to many bacteria, and manufacturing insulin has become easy and cheap in today’s world.