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Cellular Reproduction and DNA
Offspring receive their traits from their parents- but sometimes the child looks nothing like the parents
Cellular Reproduction and DNA
Offspring receive their traits from their parents- but sometimes the child looks nothing like the parents
Lamarkian biology- characteristics such as height, strength, and weight are determined by the activities of the parents. (FAIL.)
The Father of Modern Genetics
Gregor Mendel (1822-1884): an Austrian monk
Gave first real explanation for how traits are passed on to offspring
Conducted meticulous experiments on 29,000 pea plants
Mendel's work was rejected during his lifetime, and it wasn't widely accepted until the 1930's and 1940's
Genetics- the science that studies how characteristics get passed from parent to offspring
Genes, Chromosomes, and DNADNA governs an organism's
traits and characteristics
DNA's main function is to tell the cell what proteins to make
Genes, Chromosomes, and DNADNA governs an organism's
traits and characteristics
DNA's main function is to tell the cell what proteins to make
Not every organism's traits are completely determined by a person's genes
Genetic tendency- a range of possible characteristics set by DNA
Genetic Tendencies People have a certain capacity for musical ability, or athletic ability
Some people choose to fight against genetic predispositions such as alcoholism and obesity
Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both
Genetic Tendencies People have a certain capacity for musical ability, or athletic ability
Some people choose to fight against genetic predispositions such as alcoholism and obesity
Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both
Gay rights activists are searching for a “gay gene” in order to justify their behavior
However, many defects are transmitted through genes (eg. Down Syndrome, cystic fibrosis, color blindness)
Even if a “gay gene” were found, a gene cannot force a person into a homosexual lifestyle- he is able to choose how to live, just like an alcoholic can choose not to drink alcohol
Developmental Factors
Characteristics completely from DNA: hair color, blood type
DNA alone does not determine who you are or what you will become
DNA provides the general framework within which you decide who you will become
Characteristics completely from DNA: hair color, blood type
DNA alone does not determine who you are or what you will become
DNA provides the general framework within which you decide who you will become
Genetic factors- traits determined by DNA
Environmental factors- nonbiological factors that are involved in a person's surroundings (family, friends, school, choices they make)
Spiritual factors- factors in a person's life determined by the quality of their relationship with God
There is still much debate over how much influence each of these factors has over a person's development
Developmental Factors
Genes and DNA
Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait
Genes and DNA
Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait
The tasks that a cell can complete depend upon the proteins it produces
If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell
Genes and DNA
Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait
The tasks that a cell can complete depend upon the proteins it produces
If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell
A cell knows what proteins it should produce because the DNA tells it what to make
DNA and RNA
DNA and RNA
DNASugar: deoxyribose
Structure: double helix
Nucleotides: adenine, guanine, cytosine, thymine
More stable, less likely to experience changes during duplication (less mutations)
RNA
Sugar: ribose
Structure: single strand
Nucleotides: adenine, guanine, cytosine, thymine
Less stable
Protein Synthesis- Part 1: Transcription
1. Transcription- building an RNA strand from a section of DNA
RNA copies DNA by attaching corresponding nucleotide bases
RNA is like a camera that produces a negative image (light in places it should be dark)
T- A
C- G
A- U
Protein Synthesis- Part II: Translation
2. Translation: the process of translating the nucleotide bases into amino acid sequences
Protein Synthesis- Part II: Translation
2. Translation: the process of translating the nucleotide bases into amino acid sequences
Messenger RNA (mRNA)- RNA that performs transcription and then goes to the ribosomes
Protein Synthesis- Part II: Translation
2. Translation: the process of translating the nucleotide bases into amino acid sequences
Messenger RNA (mRNA)- RNA that performs transcription and then goes to the ribosomes
Transfer RNA (tRNA)- contains an anticodon bonded to an amino acid
Anticodon- three nucleotide base sequence on tRNA
Protein Synthesis- Part II: TranslationCodon- a sequence of three
nucleotide bases on mRNA that refers to specific amino acid
Protein Synthesis- Part II: TranslationCodon- a sequence of three
nucleotide bases on mRNA that refers to specific amino acid
Translation repeats until all amino acids that are called for by codons are linked together
DNA → RNA → protein
Protein Synthesis- Part II: TranslationCodon- a sequence of three
nucleotide bases on mRNA that refers to specific amino acid
Translation repeats until all amino acids that are called for by codons are linked together
DNA → RNA → protein
A given amino acid can be “called for” by several different codons. eg. cysteine can be called by UGC or UGU
However, a single codon cannot call for more than one amino acid (eg. UGU is only for cysteine)
Protein Synthesis
DNA and RNAExons- part of DNA with instructions for making a protein
Introns- separates exons, must be removed before it becomes mRNA
DNA and RNAExons- part of DNA with instructions for making a protein
Introns- separates exons, must be removed before it becomes mRNA
Introns are also known as “junk DNA” because they don't appear to serve any purpose
DNA is very thin- .0000002mm
If all the DNA from one cell we strung together end to end, it would be six feet long. All DNA in body: 67 billion miles (16x distance of Pluto to Sun)
How DNA is Packaged
Histones- proteins that act as spools which wind up small stretches of DNA
Nucleosomes- beads of DNA wrapped around histone
How DNA is Packaged
Histones- proteins that act as spools which wind up small stretches of DNA
Nucleosomes- beads of DNA wrapped around histone
Chromosome- network of DNA coils and proteins
In nucleus
How DNA is PackagedHistones- proteins that act as
spools which wind up small stretches of DNA
Nucleosomes- beads of DNA wrapped around histone
Chromosome- network of DNA coils and proteins
In nucleus
Chromatin- strands of chromosomes, RNA, and proteins
Condensed chromosome- most compact version of DNA
Humans: 46 chromosomes horse: 64, crayfish: 200
Mitosis and InterphaseMitosis- a process of asexual
reproduction in eukaryotic cells
Interphase- time interval between cellular reproduction
Chromosomes not condensed
Cell spends most of its time in this stage
DNA remains in its chromatin form, except when making proteins
Cell cycle- cycle between interphase and mitosis
Mitosis
-In order to reproduce, chromosomes must duplicate
-Sister chromatids- duplicate chromosomes
-The centrioles also duplicate, then mitosis starts
1. Prophase
-duplicated chromosomes coil into their condensed form
Centromere- the region that joins two sister chromatids
-aster- microtubules extended from centrioles
-as centrioles migrate, the microtubules grow, producing spindle fibers
- Spindle fibers make up the mitotic spindle
2. Metaphase
-chromosomes are lined up along equatorial plane
2. Metaphase
-chromosomes are lined up along equatorial plane
3. Anaphase
-microtubules separate the sister chromatids from each other
-sister chromatids are pulled to opposite sides
2. Metaphase
-chromosomes are lined up along equatorial plane
3. Anaphase
-microtubules separate the sister chromatids from each other
-sister chromatids are pulled to opposite sides
4. Telophase
-spindle begins to disintergrate
-plasma membrane begins to constrict along equatorial plane
4. Telophase
-spindle begins to disintergrate
-plasma membrane begins to constrict along equatorial plane
-two cells begin to form
-nuclear membrane forms around each chromosome
- chromosomes uncoil from their condensed form back into chromatin
-the end result is two identical daughter cells
More About Mitosis
•Each daughter cell gets at least one of each organelle
•If the two cells have only one organelle between them, the organelle is split
•DNA can build up or make new organelles as needed
•The mitochondria has its own DNA so it can replicate itself
More About Mitosis
•Each daughter cell gets at least one of each organelle
•If the two cells have only one organelle between them, the organelle is split
•DNA can build up or make new organelles as needed
•The mitochondria has its own DNA so it can replicate itself
•Mitosis is a form of asexual reproduction
•Every eukaryotic organism performs mitosis
•Mitosis produces new cells as the organism grows, and replaces dead cells
•Millions of red blood cells die every minute
More About Mitosis
• Plant mitosis: due to cell wall, the plasma membrane can’t constrict
• Cellulose is formed in the middle, producing the cell well
• Also no centrioles are in the plant cells
ChromosomesKaryotype- the figure produced when chromosomes of a species during metaphase are arranged according to their homologous pairs
-Homologous pairs- chromosomes that are very similar but not identical
-Sex chromosomes- a pair of chromosomes which can be used to
distinguish between the sexes- XX: female
- XY: male
Diploid and Haploid Cells
•each homologue has exactly the same number of genes as its partner
•For example, the gene for blood type can be found on chromosome #9- on one homologue, the gene might be for blood type A and on the other, O.
•Diploid cell- a cell with chromosomes that come in homologous pairs
•Haploid cell- a cell that has only one representative of each pair
Diploid and Haploid Cells•Even species that have diploid cells will have some haploid cells
•Diploid number (2n)- total number of chromosomes in a diploid cell
•46 for human
•Haploid number- (n) number of homologous pairs in a diploid cell
•23 for human
Sexual Reproduction
Meiosis – the process by which a diploid (2n) cell forms gametes (n)
-each parent contributes 23 chromosomes
-In meiosis, diploid cells get split into haploid cells called gametes
-Gametes- haploid cells produced by diploid cells for purpose of sexual reproduction
-Female: egg (ovum) Male: sperm
-Two gametes join together to form a|diploid cell that has 23 homologous pairs of chromosomes- zygote
Meiosis IMeiosis I- one diploid cell forms two
haploid cells
-two begin meiosis, cell must duplicate DNA and centrioles
- Prophase I- centrioles move to opposite sides of cell
- DNA is exchanged between homologous chromosomes (cross over)
- Mitotic spindle forms
- Metaphase I- single microtubule for each pair- chromatids stay intact
Meiosis I
Anaphase I- homologous pairs are pulled to either side
Telophase I- plasma membrane constricts along equatorial plane
-two haploid cells are formed
-though each cell has 46 chromosomes, the cells are considered haploid because the chromosomes are paired with an exact duplicate, leaving 23 unique chromosomes
Meiosis Prophase II- both cells have their centrioles duplicate and form a spindle
Metaphase II- chromosomes line up along equatorial plane
-chromosomes attach to each chromatid
Anaphase II- the microtubules pull the chromosomes away fromtheir duplicates
Telophase II- plasma membrane constricts along equatorial plane, forming two pairs of haploid cells
Mitosis vs. Meiosis
Mitosis: one diploid cell forms two duplicate diploid cells
Meiosis: diploid to haploid
-One diploid cell forms 4 haploid cells
Spermatogenesis
-In males, meiosis produces sperm cells
- At the end of meiosis II, flagella emerges on each of the four haploid cells
Oogenesis
Oogenesis: meiosis in females
-at the end of telophase I, one of the two cells produced takes most of the cytoplasm and organelles
-After meiosis II, one of the big cells from Meiosis I takes most of the cytoplasm and organelles
-the end result is one large gamete (Egg cell) and three smaller polar bodies
- when the sperm burrows into the egg, it forms a diploid cell called a zygote
Viruses
Virus- non-cellular infectious agent
1. has genetic material (RNA or DNA) inside a protective protein coat
2. cannot reproduce on its own
-a virus hijacks a cell in order to reproduce
-because a virus cannot reproduce on its own, it’s not alive
Lytic Pathway
1. Virus attaches to bacterium
2. Virus injects own genetic material
3. Virus DNA instructs bacteria to make viral proteins and genetic material
4. Viruses form in cell
5. Cell ruptures, releasing several viruses
Viruses
•Some viruses, like HIV, can inject genes into the cell and lie dormant for several years before the lytic pathway starts
•Viruses: chicken pox, flu, mumps, cold, mumps, measles, AIDS, cold sores, some forms of cancer
•Viruses affect plants, animals, and bacteria
The Immune System
Phagocytic cells- purpose is to engulf and destroy pathogens (eg. White blood cells)
Lymph nodes- a place for phagocytic cells to gather
-lymph carries pathogens through the lymph nodes, where the phagocytic cells destroy them
Antibodies- specialized proteins that aid in destroying infectious agents
Antibodies-some antibodies can destroy many
kinds of pathogens, others can only fight one kind
-when the body is infected, it produces antibodies that will destroy the pathogen
-the body remembers which antibodies will fight a particular disease
Vaccine- a weakened or inactive version of a pathogen that stimulates the body’s production of antibodies which can aid in destroying a pathogen