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ENVS 212 > Lecture 5: Mutation and Variation > Flashcards

Lecture 5: Mutation and Variation Flashcards

1
Q

Mutation provides ____

A

new variation

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2
Q

Without variation, ____

A

there is nothing for natural selection to act on

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3
Q

What is the main structure in the machinery of inheritance?

A

Chromosome

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4
Q

Normally chromosomes are what shape?

A

Rod-shaped

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5
Q

Gene

A

the physical unit of heridity, composed of DNA

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6
Q

What do genes code for?

A

RNA and proteins

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7
Q

What are genes used interchangeably with?

A

Locus

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8
Q

Allele

A

alternative forms of a gene

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9
Q

True or False: chromosome number varies across the natural world

A

True

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10
Q

Codon

A

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

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11
Q

Single nucleotide polymorphism (SNP)

A

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

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12
Q

Exons

A

segments of a gene that code for amino acids

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13
Q

Introns

A

noncoding DNA segments in between the exons

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14
Q

Gene expression

A

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

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15
Q

Why are genotype and phenotype not necessarily linked?

A

phenotype can be influenced by the environment as well as genetics

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16
Q

Segregation

A

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

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17
Q

Why is genetic segregation important?

A

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

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18
Q

Genotype frequencies vs Allele frequencies

A

A1A1, A1A2, A2A2
vs.
A1, A2

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19
Q

What does Hardy-Weinberg Equilibrium characterize?

A

the distributions of genotype frequencies in populations that are not evolving

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20
Q

HWE is a null model, which is?

A

a model based on what we expect due to chance alone

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21
Q

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

This is the equation for finding…

A

Genotypic frequencies after one generation of random mating

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22
Q

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

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

A

p^2 = frequency of homozygous genotypes (AA)

2pq = frequency of heterozygous genotypes (AB)

q^2 = frequency of homozygous genotypes (BB)

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23
Q

Why is p + q = 1 ?

A

There are only two possible alleles

24
Q

What are the 5 HWE conditions?

A

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)

25
Q

What does deviation from HWE mean?

A

A locus is involved in an interesting evolutionary process

26
Q

Recombination

A

Produces new genetic combinations within a gamete

27
Q

What are two ways recombination can occur?

A

Independent assortment and crossing over

28
Q

Crossing over

A

when homologous chromosomes swap segments of DNA

29
Q

Recombination rate (r)

A

The probability that recombination occurs between a given pair of loci

30
Q

If r = 1/2…

A

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

31
Q

If r < 1/2…

A

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

32
Q

Linkage disequilibrium

A

alleles are found together more often than you would expect

33
Q

When is linkage disequilibrium likely to occur?

A

when r is low

34
Q

Epistasis

A

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

35
Q

Horizontal vs Vertical gene transfer

A

HGT: the movement of DNA in organisms that reproduce asexually

VGT: the movement of DNA in organisms that reproduce sexually

36
Q

Bacterial transformation

A

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

37
Q

Point mutation

A

single base

38
Q

Which type of point mutation is usually synonymous? nonsynonymous?

A

Third position

Second position

39
Q

Insertion/deletion

A

addition/removal of base(s)

40
Q

Inversion

A

DNA segment is reversed

41
Q

Fusion

A

two chromosomes become one

42
Q

Fission

A

one chromosome breaks into two

43
Q

Pseudogene

A

non-functional genes produced by stop codons

44
Q

Whole genome duplication

A

mutation that duplicates all DNA in the genome

45
Q

When does whole genome duplication occur?

A

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

46
Q

What organisms have whole genome duplications?

A

Common in plants

47
Q

Human mutation rate

A

1 in 100,000,000

48
Q

Which organisms prefer high mutation rates?

A

Viruses and parasites

49
Q

Beneficial mutations

A

increase fitness, are rare, acted on by natural selection

50
Q

Deleterious mutations

A

decrease fitness, more common, selected against

51
Q

Pleiotropy

A

occurs when a single mutation affects multiple traits

52
Q

Mutations in gametes vs somatic cells

A

Gamete: inherited

Somatic cell: not inherited, can affect bearer

53
Q

Transitions vs transversions

A

Transitions: mutations between A and G, C and T

Transversions: all other mutations

54
Q

Are transition or transversion mutations more common?

A

transition

55
Q

Epigenetics

A

study of changes in expression of genes

56
Q

Methylation

A

prevents expression of genes

57
Q

Can methylated genes be inherited?

A

Yes

ENVS 212 (10 decks)

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