Lecture 5: Mutation and Variation

Question 1

Mutation provides ____

Answer 1

new variation

Question 2

Without variation, ____

Answer 2

there is nothing for natural selection to act on

Question 3

What is the main structure in the machinery of inheritance?

Answer 3

Chromosome

Question 4

Normally chromosomes are what shape?

Answer 4

Rod-shaped

Question 5

Gene

Answer 5

the physical unit of heridity, composed of DNA

Question 6

What do genes code for?

Answer 6

RNA and proteins

Question 7

What are genes used interchangeably with?

Answer 7

Locus

Question 8

Allele

Answer 8

alternative forms of a gene

Question 9

True or False: chromosome number varies across the natural world

Answer 9

True

Question 10

Codon

Answer 10

sets of three DNA bases that are translated to amino acids within protein-coding genes

Question 11

Single nucleotide polymorphism (SNP)

Answer 11

When a single DNA base pair different causes the difference between two alleles

Question 12

Exons

Answer 12

segments of a gene that code for amino acids

Question 13

Introns

Answer 13

noncoding DNA segments in between the exons

Question 14

Gene expression

Answer 14

The process by which a gene gets turned on in a cell to make RNA and proteins

Question 15

Why are genotype and phenotype not necessarily linked?

Answer 15

phenotype can be influenced by the environment as well as genetics

Question 16

Segregation

Answer 16

The separation of alleles during meiosis so that each gamete carries only one allele for each gene

Question 17

Why is genetic segregation important?

Answer 17

With segregation, all alleles in a given individual have an equal chance of being inherited in the next generation

Question 18

Genotype frequencies vs Allele frequencies

Answer 18

A1A1, A1A2, A2A2
vs.
A1, A2

Question 19

What does Hardy-Weinberg Equilibrium characterize?

Answer 19

the distributions of genotype frequencies in populations that are not evolving

Question 20

HWE is a null model, which is?

Answer 20

a model based on what we expect due to chance alone

Question 21

p^2 + 2pq + q^2 = 1

This is the equation for finding…

Answer 21

Genotypic frequencies after one generation of random mating

Question 22

p^2 + 2pq + q^2 = 1

p^2 = ?
2pq = ?
q^2 = ?

Answer 22

p^2 = frequency of homozygous genotypes (AA)

2pq = frequency of heterozygous genotypes (AB)

q^2 = frequency of homozygous genotypes (BB)

Question 23

Why is p + q = 1 ?

Answer 23

There are only two possible alleles

Question 24

What are the 5 HWE conditions?

Answer 24

1) mating is random

2) population size is “infinite”

3) gene flow does not occur

4) mutation does not occur

5) locus concerned is not under selection (no fitness difference between alleles)

Question 25

What does deviation from HWE mean?

Answer 25

A locus is involved in an interesting evolutionary process

Question 26

Recombination

Answer 26

Produces new genetic combinations within a gamete

Question 27

What are two ways recombination can occur?

Answer 27

Independent assortment and crossing over

Question 28

Crossing over

Answer 28

when homologous chromosomes swap segments of DNA

Question 29

Recombination rate (r)

Answer 29

The probability that recombination occurs between a given pair of loci

Question 30

If r = 1/2...

Answer 30

50% chance that when an individual makes a gamete that one of the chromosomes it carries will be from the mother and the other from the father

Question 31

If r < 1/2...

Answer 31

two loci are on the same chromosome. smaller r = closer loci

Question 32

Linkage disequilibrium

Answer 32

alleles are found together more often than you would expect

Question 33

When is linkage disequilibrium likely to occur?

Answer 33

when r is low

Question 34

Epistasis

Answer 34

when the effect of an allele at one locus depends on the allele at a second locus

Question 35

Horizontal vs Vertical gene transfer

Answer 35

HGT: the movement of DNA in organisms that reproduce asexually VGT: the movement of DNA in organisms that reproduce sexually

Question 36

Bacterial transformation

Answer 36

A donor bacterial cell releases DNA that is taken up by a recipient bacterial cell. This is an example of HGT.

Question 37

Point mutation

Answer 37

single base

Question 38

Which type of point mutation is usually synonymous? nonsynonymous?

Answer 38

Third position Second position

Question 39

Insertion/deletion

Answer 39

addition/removal of base(s)

Question 40

Inversion

Answer 40

DNA segment is reversed

Question 41

Fusion

Answer 41

two chromosomes become one

Question 42

Fission

Answer 42

one chromosome breaks into two

Question 43

Pseudogene

Answer 43

non-functional genes produced by stop codons

Question 44

Whole genome duplication

Answer 44

mutation that duplicates all DNA in the genome

Question 45

When does whole genome duplication occur?

Answer 45

when meiosis produces gametes that carry a diploid genome which then undergo fertilization

Question 46

What organisms have whole genome duplications?

Answer 46

Common in plants

Question 47

Human mutation rate

Answer 47

1 in 100,000,000

Question 48

Which organisms prefer high mutation rates?

Answer 48

Viruses and parasites

Question 49

Beneficial mutations

Answer 49

increase fitness, are rare, acted on by natural selection

Question 50

Deleterious mutations

Answer 50

decrease fitness, more common, selected against

Question 51

Pleiotropy

Answer 51

occurs when a single mutation affects multiple traits

Question 52

Mutations in gametes vs somatic cells

Answer 52

Gamete: inherited Somatic cell: not inherited, can affect bearer

Question 53

Transitions vs transversions

Answer 53

Transitions: mutations between A and G, C and T Transversions: all other mutations

Question 54

Are transition or transversion mutations more common?

Answer 54

transition

Question 55

Epigenetics

Answer 55

study of changes in expression of genes

Question 56

Methylation

Answer 56

prevents expression of genes

Question 57

Can methylated genes be inherited?

Answer 57

Yes