Chapter 12 - Genetics and Evolution

Question 1

Define Chromosomes

Answer 1

Chromosomes contain genes in a linear sequence

Question 2

Define Alleles

Answer 2

Alleles are alternate forms of a gene.

Question 3

Dominant vs. Recessive Alleles

Answer 3

Dominant requires only one copy to be expressed; Recessive requires two copies to be expressed

Question 4

What is a Genotype?

Answer 4

The combination of alleles one has at a given genetic locus.

Question 5

Homozygous vs. Heterozygous vs. Hemizygous

Answer 5

Homo: two of the same alleles
Hetero: two different alleles
Hemi: only one allele

Question 6

What is a Phenotype?

Answer 6

An observable manifestation of a genotype

Question 7

What is Complete Dominance?

Answer 7

When the effects of one allele completely masks the effect of another.

Question 8

What is Codominance?

Answer 8

More than one dominant allele present.

Question 9

What is Incomplete Dominance?

Answer 9

Has no dominant alleles; heterozygotes have intermediate phenotypes

Question 10

What is Penetrance?

Answer 10

The proportion of a population with a given genotype who express the phenotype.

Question 11

What is Expressivity?

Answer 11

Refers to the varying phenotypic manifestations of a given genotype.

Question 12

What does Mendel’s First Law (of Segregation) state?

Answer 12

An organism has two alleles for each gene, which segregates during meiosis, resulting in gametes carrying only one allele for a trait.

Question 13

What does Mendel’s Second Law (of Independent Assortment) state?

Answer 13

The inheritance of one allele does not influence the probability of inheriting an allele for a different trait.

Question 14

Describe the Griffith Experiment

Answer 14

Demonstrated the transforming principle, converting non-virulent live bacteria into virulent bacteria by exposure to heat-killed virulent bacteria.

Question 15

Describe the Avery-McLeod-McCarthy Experiment

Answer 15

Demonstrated that DNA is the genetic material because degradation of DNA led to a cessation of bacterial transformation.

Question 16

Describe the Hershey- Chase Experiment

Answer 16

Confirmed that DNA is the genetic material because only radiolabeled DNA could be found in bacteriophage-infected bacteria.

Question 17

What do all of the alleles in a given population constitute?

Answer 17

The Gene Pool

Question 18

What are Mutations?

Answer 18

Changes in DNA sequence

Question 19

What do Nucleotide Mutations include?

Answer 19

Point mutations (the substituting of one nucleotide for another) and Frameshift mutations (moving the three-letter transcriptional reading frame)

Question 20

What are Silent Mutations?

Answer 20

Have no effect on the protein

Question 21

What are Missense Mutations?

Answer 21

Results in substitution of one amino acid for another

Question 22

What are Nonsense Mutations?

Answer 22

Results in the substitution of a stop codon for an amino acid.

Question 23

What do Insertions and Deletions result in?

Answer 23

A shift in the reading frame, leading to changes for all downstream amino acids.

Question 24

What are Deletion Mutations?

Answer 24

Occur when a large segment of DNA is lost.

Question 25

What are Duplication Mutations?

Answer 25

Occur when a segment of DNA is copied multiple times.

Question 26

What are Inversion Mutations?

Answer 26

Occur when a segment of DNA is reversed.

Question 27

What are Translocational Mutations?

Answer 27

Occur when a segment of DNA is swapped with a segment of DNA from another chromosome.

Question 28

What is Genetic Leakage?

Answer 28

A flow of genes between species through hybrid offspring.

Question 29

What is Genetic Drift?

Answer 29

Occurs when the composition of the gene pool changes as a result of a chance

Question 30

What is the Founder Effect?

Answer 30

Results from bottlenecks that suddenly isolate a small population, leading to inbreeding and increases prevalence of certain homozygous genotypes.

Question 31

What are the two types of Frameshift Mutations?

Answer 31

Insertion an Deletion

Question 32

What is the purpose of Punnett Squares?

Answer 32

They visually represent the crossing of gametes from parents to show relative genotypical and phenotypical frequencies. Parental generation is represented by P; filial (offspring) generations are represented by F1, F2 and so on.

Question 33

What do monohybrid and dihybrid crosses account for? What about sex-linked crosses?

Answer 33

Mono: accounts for one gene.
Di: accounts for two genes.
Sex-linked: sex chromosomes are usually used to indicate sex as well as a genotype.

Question 34

What ratio does crossing two heterozygotes for a trait with complete dominance result in?

Answer 34

1:2:1 ratio of genotypes and 3:1 ratio of phenotypes

Question 35

What is the Recombination Frequency (theta)?

Answer 35

The likelihood of two alleles being separated during crossing over in meiosis.

Question 36

What are Genetic Maps?

Answer 36

Can be made using recombination frequency as the scale in centimorgans.

Question 37

What does the Harvey-Weinberg principle state?

Answer 37

If a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant (Hardy-Weinberg Equilibrium) **key concept p. 451

Question 38

What is Natural Selection?

Answer 38

States that chance variations exist between individuals and that advantageous variations - those that increase an individuals fitness for survival or adaptation to the environment - afford the most opportunities for reproductive success.

Question 39

What does the Modern Synthesis Model (Neo-Darwinism) account for?

Answer 39

Accounts for mutation and recombination as mechanisms of variation and considers differential reproduction to be the mechanism for reproductive success.

Question 40

What is Inclusive Fitness?

Answer 40

Considers an organisms success to be based on the number of offspring, and the ability of the offspring to then support others; survival of offspring or relatives ensures appearance of genes in subsequent generations.

Question 41

What is Punctual Equilibrium?

Answer 41

Considers evolution to be a very slow process with intermittent rapid bursts of evolutionary activity.

Question 42

What do different types of selection lead to?

Answer 42

Changes in Phenotypes

Question 43

What does Stabilizing Selection do?

Answer 43

Keeps phenotypes in narrow range, excluding extremes.

Question 44

What does Directional Selection do?

Answer 44

Moves the average phenotype toward one extreme.

Question 45

What does Disruptive Selection do?

Answer 45

Moves the population toward two different phenotypes at the extremes and can lead to speciation.

Question 46

What is Adaptive Radiation?

Answer 46

The rapid emergence of multiple species from a common ancestor, each of which occupies its own ecological niche.

Question 47

What is a Species?

Answer 47

The largest group of organisms capable of breeding to form fertile offspring. Species are reproductively isolated from each other by pre- or post zygotic mechanisms.

Question 48

What is Divergent Evolution?

Answer 48

Occurs when two species sharing a common ancestor become more different.

Question 49

What is Parallel Evolution?

Answer 49

Occurs when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures.

Question 50

What is Convergent Evolution?

Answer 50

Occurs when two species not sharing a recent ancestor evolve to become similar due to analogous selection pressures.

Question 51

What does the Molecular Clock Model state?

Answer 51

The degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor.