Lecture 2 & 3

Question 1

Describe the research conducted by Peter and Rosemary Grant.

Answer 1

Determined that natural selection is variable over time and can result in rapid evolutionary change by tracking the beak sizes of the medium ground finch over the course of generations. A severe drought resulted in only harder, woody seeds being available to birds; finches with bigger beaks had a better change of surviving the drought, so the next generation inherited larger beaks on average. Heavy rain came to the island a few years later and produced a significant number of small seeds, so smaller beaks became favored.

Question 2

What is a gene?

Answer 2

a segment of DNA whose nucleotide sequence regulates the expression of other genes

Question 3

What are alleles?

Answer 3

two or more DNA sequences occurring at a particular gene locus

Question 4

What is a genotype, and what are the three types of genotypes?

Answer 4

the genetic makeup of an individual organism
homozygous dominant (PP), homozygous recessive (pp), heterozygous (Pp)

Question 5

What is a phenotype?

Answer 5

observable, measurable characteristics that occur as a result of a genotype

Question 6

What is complete dominance?

Answer 6

the dominant allele completely masks the phenotypical effects of the recessive alleles; typically giving rise to just two different phenotypes

Question 7

What is incomplete dominance?

Answer 7

incomplete dominance - both alleles of a gene at a locus are partially expressed, typically resulting in a variety of intermediate phenotypes

Question 8

What is a population?

Answer 8

a group of individuals from the same species restricted to one area

Question 9

What is the relationship between genetic variation and environmental change?

Answer 9

the more genetic variation within a population, the better equipped it is to respond to environmental change

Question 10

What is adaptive evolution, and what is the mechanism that causes it?

Answer 10

the frequency of an advantageous trait in a population increases over time, and the favorable trait is continuously changing depending on shifting environmental pressures; caused by natural selection

Question 11

What is evolution?

Answer 11

a change in allele frequencies in a population across generations

Question 12

What is a mutation?

Answer 12

a change in the nucleotide sequence of an organism’s DNA; can create new alleles; considered the ultimate source of all genetic variation

Question 13

What is gene expression?

Answer 13

the information in genes used by cells to produce proteins; mistakes in gene expression can give rise to mutations

Question 14

What are the two types of mutations?

Answer 14

somatic mutations - affects cells in the body (soma) of an organism; not heritable in animals, but can be passed down during vegetative reproduction in plants
germline mutations - affects gametes (eggs, sperm) of an individual; heritable genetic variation that is relevant to evolution

Question 15

What is one way that gene expression is regulated?

Answer 15

complementary base pairs: only particular base pairs can form hydrogen bonds between them to make DNA double stranded and able to form helix structure
guanine + cytosine; thymine + adenine

Question 16

What is genetic drift?

Answer 16

a change in the gene pool of a population due to chance, not due to the selection of a favorable trait (i.e. a moose trampling flowers); results from random sampling error, which is higher with a smaller sample; reduces genetic variation in a population and alters allele frequencies

Question 17

What is a fixed allele? What is a lost allele? What is the gene allele frequency for each? How does this relate to loci?

Answer 17

alleles that become a permanent part of the population, as opposed to lost alleles; gene allele frequency of a fixed allele is 100%; gene allele frequency of a lost allele is 0%; fixed and lost genes cannot be from the same locus - they are different alleles from multiple loci

Question 18

What is a bottleneck? Provide an example.

Answer 18

an event that drastically reduces the size of a population and results in a non-representative set of alleles for subsequent populations, even after the population size rebounds (i.e. elephant seals)

Question 19

What factors determine the probability of an allele making it through a bottleneck?

Answer 19

1. the frequency of the allele before the bottleneck (rare alleles are more likely to be lost)
2. the severity of the bottleneck (the severity of the population size drop during the bottleneck)

Question 20

What is the founder effect? Provide an example.

Answer 20

a type of bottleneck resulting from a small number of individuals colonizing a new, isolated habitat (i.e. silvereye birds)

Question 21

What is gene flow? Provide an example.

Answer 21

the transfer of alleles from one population to another, as a result of movement of individuals or gametes (i.e. common house mosquito, or pollen)

Question 22

How does gene flow effect populations?

Answer 22

introduces variation into a new population; causes populations of the same species to become more homogenous to each other, but overall diversity still increases

Question 23

What is recombination? How does it effect populations?

Answer 23

pieces of DNA are broken and recombined to produce new populations of alleles; generates variation and genetic diversity (along with mutations)

Question 24

What is independent assortment? How does it effect populations?

Answer 24

states that the allele a gamete receives for one gene does not influence the allele received for another gene; ensures novel combinations of alleles