Module B Review

2nd Quarterly Assessment ReviewUnits 6 & 7

BIO.B.2.2

• Explain the process of protein synthesis (i.e., transcription, translation, and protein modification).

• Describe how the processes of transcription and translation are similar in all organisms.

• Describe the role of ribosomes, endoplasmic reticulum, Golgi apparatus, and the nucleus in the production of specific types of proteins.

• RNA RNA differs from DNA in three major ways.

– DNA has a deoxyribose sugar, RNA has a ribose sugar.– RNA has uracil instead of thymine (found in DNA)

– A pairs with U– DNA is a double stranded molecule, RNA is single-stranded.

TRANSCRIPTION & TRANSLATION: To make a protein from DNA using RNA.

start site

5. nucleotides

transcription complex

6. RNA

codon formethionine (Met)

codon forleucine (Leu)

• Translation aka: Protein Synthesis

• BIO. B.2.1: Describe processes that can alter composition or number of chromosomes (i.e., crossing over, nondisjunction, duplication, translocation, deletion, insertion, and inversion).

• BIO.B.2.3 : Explain how genetic information is expressed. • Describe how genetic mutations alter the DNA sequence and

may or may not affect phenotype (e.g., silent, nonsense, frame shift).

Some mutations affect a single gene, while others affect an entire chromosome.

A gene mutation affects a single gene. • Many kinds of mutations can occur, especially during

replication.

Types of Gene Mutations:• A point mutation substitutes one nucleotide for

another. Ex: Sickle Cell Anemia

mutatedbase

Nonsense Mutation• Type of point mutation• Results in a premature stop codon

and usually a nonfunctional protein

• A frame-shift mutation inserts or deletes a nucleotide in the DNA sequence. Throws off the reading frame.

• THE CAT ATE THE RAT• THC ATA TET HER AT

• Chromosomal mutations affect many genes and an entire chromosome. Chromosomal mutations may occur during crossing over.

DeletionDue to breakageA piece of a chromosome is lost

Inversion

Chromosome segment breaks offSegment flips around backwardsSegment reattaches

• Translocation results from the exchange of DNA (piece of one chromosome) segments between non-homologous chromosomes.

NondisjunctionFailure of chromosomes to separate

during meiosisCauses gamete to have too many or

too few chromosomes

Nondisjunction Can cause “Trisomy” (three copies of the same

chromosome in an egg or sperm)Trisomy 21 (Down syndrome)

• Gene duplication results from unequal exchange of segments crossing over. Results in one chromosome having 2 copies of some genes and the other chromosomes having no copies of those genes.

Several methods help map human chromosomes.

• A karyotype is a picture of all chromosomes in a cell.

X Y

BIO.B.2.4

• Apply scientific thinking, processes, tools, and technologies in the study of genetics.

• Explain how genetic engineering has impacted the fields of medicine, forensics, and agriculture (e.g., selective breeding, gene splicing, cloning, genetically modified organisms, gene therapy).

9.1: Manipulating DNA

• Key Concept: – Biotechnology relies on cutting DNA at specific

places.

Restriction sites

A DNA fingerprint is a type of restriction map.

• DNA fingerprints are based on parts of an individual’s DNA that can be used for identification– Based on noncoding regions of DNA– Noncoding regions have repeating DNA sequences– Number of repeats differs between people– Banding pattern on a gel is a DNA fingerprint

DNA fingerprinting is used for identification.

• DNA fingerprinting depends on the probability of a match.– Many people have the same number of repeats in a

certain region of DNA– The probability that two people share identical numbers of

repeats in several locations is very small (only one chance in over 5 million people that they would match)

– Several regions of DNA are used to make a DNA fingerprint.

Uses of DNA Fingerprinting

• Evidence in criminal cases• Paternity tests• Immigration requests• Studying biodiversity• Tracking genetically modified crops

Cloning

• A clone is a genetically identical copy of a gene or an organism

• Cloning occurs in nature– Bacteria (binary fission)– Some plants (from roots)– Some simple animals (budding, regeneration)

Pros/Cons of Cloning

Benefits• Organs for transplant into

humans• Save endangered species• Reproduce beneficial traits

Concerns• Low success rate• Clones “imperfect” and less

healthy than original animal• Decreased biodiversity

Genetic Engineering/Gene Splicing

• Involves changing an organism’s DNA to give it new traits• Based on the use of recombinant DNA

– Recombinant DNA contains DNA from more than one organism

(bacterial DNA)

Uses of Genetic Engineering

• Transgenic bacteria can be used to produce human proteins– Bacteria can be used to produce human insulin for diabetics

• Transgenic plants are common in agriculture– transgenic bacteria infect a plant– plant expresses foreign gene– many crops are now genetically modified

(GM)

• Transgenic animals are used to study diseases and gene functions

Theories of geologic change set the stage for Darwin’s theory.

• There were three theories of geologic change:– Catastrophism: natural disasters such as floods and

volcanic eruptions have shaped landforms and caused species to become extinct.

– Gradualism: changes in landforms resulted from slow changes over a long period of time

– Uniformitarianism: the geologic processes that shape Earth are uniform through time

Darwin observed differences among island species.

• Variation: difference in a physical trait– Galapagos tortoises that live in areas with tall plants have long necks and long legs– Galapagos tortoises that live in areas with low plants have short necks and short

legs– Galapagos finches (Darwin’s finches) that live in areas with hard-shelled nuts have

strong beaks– Galapagos finches that live in areas with insects/fruit have long, thin beaks

• Adaptation: feature that allows an organism to better survive in its environment– Species are able to adapt to

their environment– Adaptations can lead to

genetic change in a population

Several key insights led to Darwin’s idea for natural selection.

• Natural selection: mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals

• Heritability: ability of a trait to be passed down• There is a struggle for survival due to

overpopulation and limited resources• Darwin proposed that adaptations arose over

many generations

Fossils & the Fossil Record

• Shows how species changed their form/shape over time• Ways of dating fossils:

– Relative dating: estimates the age of fossils by comparing fossil to others in the same layer of rock

• Pro: can be used if there is no other way to tell the age of the fossil• Con: layers of rock can be shifted by natural events (earthquakes,

mudslides, etc.) and this can mess up estimate

– Radiometric dating: uses the decay of radioactive isotopes (carbon-14 changes into carbon-12)

• Pro: can give an accurate age• Con: can’t give an age for really old fossils (if all isotopes have decayed)

Biogeography• Island species most closely resemble

nearest mainland species• Populations can show variation from one

island to another• Example: rabbit fur vs. climate

Embryology

• Similar embryos, diverse organisms

• Identical larvae, diverse adult body forms

• Gill slits and “tails”as embryos

Larva

Adult barnacleAdult crab

Homologous Structures

• Similar in structure, different in function• Evidence of a common ancestor• Example: bones in the forelimbs of different

animals (humans, cat legs, whale fins, bat wings)

Vestigial Organs/Structures

• Remnants of organs or structures that had a function in an early ancestor but have lost their function over time

• Evidence of a common ancestor• Examples:

– Human appendix & tailbone– Wings on flightless birds (ostrich, penguins)– Hindlimbs on whales, snakes

Molecular Biology• Common genetic code (A, T, C, & G)• Similarities in DNA, proteins, genes,

& gene products• Two closely related organisms will

have similar DNA sequences & proteins

11.1 – Genetic Variation Within Populations

• Key Concept:– A population shares a common gene pool.

Directional Selection

• Favors phenotypes at one extreme

Stabilizing Selection

• Favors the intermediate phenotype

Disruptive Selection

• Favors both extreme phenotypes

Gene Flow• Movement of alleles between populations• Occurs when individuals

join new populations and reproduce

• Keeps neighboring populations similar

• Low gene flow increases the chance that two populations will evolve into different species

bald eagle migration

Genetic Drift• Change in allele frequencies due to chance• Causes a loss of genetic diversity• Common in small populations• Bottleneck Effect is genetic

drift after a bottleneck event– Occurs when an event

drastically reduces population size

Sexual selection occurs when certain traits increase mating success.

• Sexual selection– Occurs due to higher cost of reproduction for females

• Males produce sperm continuously• Females are more limited in potential offspring each cycle

– Two types:• Intrasexual selection: competition among males• Intersexual selection: males display certain traits to females

Species can become extinct.

• Extinction: elimination of a species from Earth– Background extinction– Mass extinction