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Genetics and Developmental Biology > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

What is population genetics?

A

Population genetics is the study of genetic diversity.

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2
Q

What is an SNP (single nucleotide polymorphism)?

A

A single nucleotide polymorphism is a single base change in the DNA sequence.

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3
Q

How do you know if a mutation is a polymorphism or a rare variant?

A

The mutation is a polymorphism if the frequency is greater than 1%, and a rare variant if the frequency is less than 1%.

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4
Q

What mutations are associated with a change in DNA sequence length?

A

Insertion and deletion mutations are associated with a change in the DNA sequence length.

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5
Q

What is a missense mutation?

A

A missense mutation is a single base mutation leading to a change in 1 amino acid.

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6
Q

What is a nonsense mutation?

A

A nonsense mutation is a single base mutation in which the amino acid change results in the formation of an early stop codon. (UGA)

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7
Q

What is a silent mutation?

A

A silent mutation is a single base mutation that does not affect the amino acid that is coded for.

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8
Q

What is a frameshift mutation?

A

A frameshift mutation is when INDELS (insertions/deletions) cause the entire downstream amino acid sequence to change.

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9
Q

What does copy number variation refer to?

A

Copy number variation refers to change in the number of repetitive sequences of DNA in eukaryotes, such as:

  • Tandem repeats like micro and minisatellites.
  • Interspersed repeats such as transposons.
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10
Q

What is the difference between tandem and interspersed repeats?

A

Tandem repeats are right next to each other whilst interspersed repeats are spread out.

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11
Q

What is aneuploidy?

A

Aneuploidy is missing a whole chromosome.

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12
Q

What is trisomy?

A

Trisomy is having three copies of a chromosome.

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13
Q

What is an inversion mutation?

A

An inversion mutation is when a segment of the DNA code is switched around.

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14
Q

What is an allele?

A

An allele is an alternative form of a gene that is located at a specific position on a specific chromosome.

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15
Q

What are codominant alleles?

A

Codominant alleles refer to when both alleles are fully expressed in a heterozygote, both alleles contribute to the phenotype of the heterozygote.

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16
Q

What is a haplotype?

A

A haplotype refers to a set of linked genes that tend to be inherited together in blocks.

  • SNPs do not assort independently because they are so close together on the chromosome.
  • The block is not interrupted by genetic recombination during meiosis.
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17
Q

What is linkage disequilibrium?

A

Linkage disequilibrium is the nonrandom association of alleles at different loci.

1 = 100% inherited together, 0 = never inherited together.

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18
Q

Interpret the following D’ values:

D’ = 1
D’ is a positive number.
D’ = 0

A

D’=1 = strong Linkage disequilibrium; alleles inherited together 100% of the time

D’ is a positive number = intermediate Linkage disequilibrium, alleles inherited together some of the time

D’=0 = no Linkage disequilibrium, alleles never inherited together

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19
Q

What are isoschizomers?

A

Isoschizomers are different enzymes that recognise the same sequence and cleave it in the same way.

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20
Q

What are neoschizomers?

A

Neoschizomers are different enzymes that recognize the same sequence and cleave it in different ways.

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21
Q

What does “S” stand for as a measure of genetic diversity?

A

S = Number of segregating sites. (Sites where bases are not identical)

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22
Q

What does “P” stand for as a measure of genetic diversity?

A

P = Proportion of polymorphism.

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23
Q

What does “pi” stand for as a measure of genetic diversity?

A

pi = nucleotide diversity or average pairwise difference. (Average number of nucleotide differences per site between two randomly selected DNA sequences).

  • the likelihood of heterozygosity when comparing 2 randomly selected chromosomes from a population.
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24
Q

What does H stand for as a measure of genetic diversity?

A

H is the probability that at a single locus, any 2 alleles chosen at random from the population, will be different to each other

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25
Q

What is microevolution?

A

Microevolution refers to small scale changes within populations or species.

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26
Q

What is macroevolution?

A

Macroevolution refers to large scale changes across species.

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27
Q

What is a species?

A

A species is a group of actual or potentially interbreeding organisms that are reproductively isolated in nature from other groups.

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28
Q

What is a population?

A

A population is a group of organisms of the same species that live in a particular area.

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29
Q

What is speciation?

A

Speciation is the formation of new species.

-Anagenesis
-Cladogenesis

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30
Q

What is anagenesis?

A

Anagenesis is an evolutionary change of a single lineage in which one taxon is replaced by another without branching.

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31
Q

What is cladogenesis?

A

Cladogenesis is an evolutionary change of a particular species in which new species are branched off from a common ancestral species.

32
Q

When are new species formed?

A

New species are formed when one part of a population becomes reproductively isolated from another part
of the population

33
Q

Reproductive isolation drives speciation, what are the two types of reproductive isolation?

A

Prezygotic isolating mechanisms and postzygotic isolating mechanisms.

34
Q

What are prezygotic isolating mechanisms?

A

Prezygotic isolating mechanisms prevent organisms from mating in the first place, no zygote is ever formed.

  • Geographic mechanism
  • Temporal mechanism (incompatible mating seasons)
  • Behavioral mechanism
  • Physiological mechanism
35
Q

What are postzygotic isolating mechanisms?

A

Postzygotic isolating mechanisms refer to when mating and fertilization occur but the zygotes are non-viable or sterile.

  • Developmental sterility. (Hybrids are sterile due to abnormal gonad development)
  • Segregational sterility (Hybrids are sterile because of abnormal chromosome segregation)
36
Q

There are three types of geographically related speciation, what are they?

A
  1. Allopatric speciation.
  2. Sympatric speciation.
  3. Parapatric speciation.
37
Q

What is allopatric speciation?

A

Allopatric speciation is when species diverge from each other due to geographic isolation.

38
Q

What is sympatric speciation?

A

Sympatric speciation is the evolution of new species from a surviving ancestral species while both continue to inhabit the same geographic region.

39
Q

What is parapatric speciation?

A

Parapatric speciation is the evolution of geographically adjacent populations into distinct species.

40
Q

What are hominids?

A

Hominids refer to a large group that includes all the great apes, past and present, including chimps, humans, guerillas, and orangutangs.

41
Q

What are hominins?

A

Hominins are a group of direct but extinct ancestors of humans, as well as modern humans.

42
Q

What is a haplogroup?

A

A haplogroup is a group of haplotypes.

43
Q

What is phylogenetics?

A

Phylogenetics is the study and reconstruction of evolutionary history/relationships among a group of organisms or a set of DNA sequences.

44
Q

What are orthologs?

A

Orthologs are genes that are similar in different species because they are the result of a speciation event.

45
Q

What are paralogs?

A

Paralogs are similar genes that are the result of a gene duplication event within a species.

46
Q

What are homologs?

A

Homologs are a general term referring to the similarity of genes due to any common ancestry. Both orthologs and paralogs are homologs.

47
Q

What is topology?

A

Topology refers to the branching structure of a phylogenic tree.

48
Q

What are phylogenetic trees?

A

Phylogenetic trees are mathematical structures, representing genealogical history.

49
Q

What is a clade?

A

A monophyletic group that consists of a common ancestor and all its descendants

50
Q

What is an outgroup (used to root unrooted trees)?

A

An outgroup is a more distantly related organism that serves as a reference group when determining the evolutionary relationships of the ingroup.

51
Q

What does HWE describe?

A

HWE describes the relationship between allele frequencies and genotype frequencies in an ideal population.

  • Infinitely large population.
  • Random mate selection.
  • No mutation.
  • No migration.
  • No selection.
52
Q

What is mutation?

A

Mutation is the origin of new genetic capabilities in populations, the ultimate source of genetic variation

53
Q

What is natural selection?

A

Natural selection is the process of evolutionary adaptation whereby the genotypes best suited to survive and reproduce in a particular environment give rise to a disproportionate share of the offspring.

54
Q

What is migration?

A

Migration is the movement of organisms among subpopulations.

55
Q

What is genetic drift?

A

Genetic drift is random, undirected changes in allele frequency.

56
Q

List some causes of mutation.

A
  • Replication errors.
  • Chemical damage.
  • Radiation damage.
  • Transposition.
  • Viral insertion.
  • Unequal crossing over.
57
Q

What is the mutation rate?

A

The mutation rate refers to the number of new mutations produced in a given gene per number of gametes or per generation.

u = the number of newly affected / number of chromosomes in the population.

u per nucleotide = the number of newly affected / number of nucleotides.

58
Q

What is admixture?

A

Admixture is the result of interbreeding between two or more previously isolated populations.

  • New population is a hybrid.
59
Q

What is hybrid vigour?

A

Hybrid vigour or heterosis, is the improved or increased function of any biological quality in a hybrid offspring.

60
Q

What is intogression?

A

Introgression, refers to the movement of a gene (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with
one of its parent species.

61
Q

What is (Ne) effective population size?

A

The effective population size Ne is defined as the number of individuals in a population with an equal probability of contributing gametes to the next generation

62
Q

What are the effects of admixture on genes?

A
  • Gain of heterozygosity in hybrid pop compared to parent pops
  • Gene swamping: admixture has been known to slow local adaptation by introducing foreign, unadapted genotypes
  • Hybrid vigour or heterosis, is the improved or increased function of any biological quality in a hybrid offspring. E.g. In plants causes increased rapidity of growth, its height and general robustness
  • Introgression, refers to the movement of a gene (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species.
63
Q

What are the different mating strategies?

A
  • Monogamy: one mate
  • Polygamy: many mates
  • Polygyny: one male with many female mates
  • Polyandry : one female with many male mates
  • the mating system of humans is considered to be moderately polygynous
64
Q

What is genetic distance?

A

Genetic distance is a measure of the genetic divergence between species, or of the genetic divergence between populations within a species.

65
Q

What is positive assortive mating?

A

Positive assortive mating: similar genotypes are more likely
to mate than different genotypes

66
Q

What is negative assortive mating?

A

Negative assortive mating: different genotypes are more
likely to mate than similar genotypes

67
Q

What is the Wahlund effect?

A

Wahlund effect refers to the reduction of heterozygosity in a population caused by subpopulation structure.

68
Q

What is random mating?

A

Random Mating – mating without regard to
genotype

69
Q

What is non-random mating?

A

Non random mating: choosing specific genotypes
in mates

70
Q

What is average expected heterozygosity (He)?

A

Average expected Heterozygosity (He) is the probability that at a single locus, any 2 alleles chosen at random from the population, will be different to each other

71
Q

What is panmixia?

A

panmixia (all individuals free to breed with all other individuals)

72
Q

What is fitness?

A

Fitness: is the quantification of an individuals’ contribution to future generations / What % of a particular genotype survive

73
Q

What is positive selection?

A

positive selection =increase in rare beneficial variants that improve optimal fitness; selected allele increases in frequency

74
Q

What is negative selection?

A

negative selection =removal of harmful variants; selected allele decreases in frequency.

also called purifying selection

75
Q

What is sexual selection?

A

Sexual selection is selection in favour of a particular phenotype that signals reproductive fitness

Genetics and Developmental Biology (3 decks)

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