Chapter 12- Genetics and Evolution Flashcards

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1
Q

homologues

A

each human possesses two copies of each chromosome (except the male sex chromosome)

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2
Q

hemizygous

A

genotypical situation in which only one allele is present for a given gene (as is the case for parts of the X chromosome in males)

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3
Q

incomplete dominance

A

heterozygote expresses a phenotype that is intermediate between the two homozygous geneotypes.

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4
Q

codominance

A

more than one dominant allele exists for a given gene

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5
Q

penetrance

A

population measure. proportion of individuals in the population carrying the allele who actually express the phenotype

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6
Q

expressivity

A

different manifestations of the same genotype across the population

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7
Q

two mechanisms that allow for greater genetic diversity in offspring

A

segregation and independent assortment (also crossing over)

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8
Q

transforming principle

A

nonvirulent bacteria acquired the ability to form smooth capsules from the dead virulent bacteria (Griffiths experiment)

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9
Q

transposons

A

small piece of DNA that can insert/remove itself from DNA

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10
Q

silent mutation

A

change in nucleotide has no effect on final protein synthesized from the gene

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11
Q

degeneracy

A

wobble in genetic code in the third nucleotide of a codon

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12
Q

missense mutation

A

change in nucleotide results in substituting one amino acid for another in the final protein

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13
Q

nonsense mutations

A

occur when change in nucleotide results in substituting a stop codon for an amino acid in the final protein

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14
Q

chromosomal mutations

A

larger-scale mutations in which larger segments of DNA are affected

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15
Q

translocation mutations

A

occur when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome

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16
Q

deleterious

A

detrimental (one class is “inborn errors of metabolism)

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17
Q

inborn errors of metabolism

A

class of deleterious mutations. defects in genes required for metabolism.

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18
Q

genetic leakage

A

flow of genes between species

19
Q

genetic drift

A

changes in composition of the gene pool due to chance. more common in smaller populations

20
Q

founder effect

A

more extreme case of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations as a result of a natural barrier/bottlenecks

21
Q

bottlenecks

A

drastically and suddenly reduce size of population available for breeding

22
Q

what can decrease genetic diversity?

A

genetic drift, the founder effect, inbreeding

23
Q

inbreeding depression

A

loss of genetic variation may cause reduced fitness of the population

24
Q

outbreeding/ outcrossing

A

introduction of unrelated individuals into a breeding group

25
Q

what do P and F stand for?

A

P generation- parent

F generation- filial (offspring)

26
Q

test cross/ back crosses

A

when determining an unknown genotype you cross the unknown organism with one that is known to be homozygous recessive

27
Q

unless told otherwise, what is always assumed about X-linked (sex-linked) traits?

A

that they are recessive (ex: hemophilia)

28
Q

recombination frequency

A

the likelihood that two alleles are separated from each other during crossing over (roughly proportional to the distance between the genes on the chromosome)

29
Q

in a genetic map what is a map unit and what does it correspond to?

A

map unit = centimorgan, which corresponds to 1% chance of recombination occurring between two genes.

30
Q

5 criteria met for Hardy-Weinberg equilibrium

A

MEANS THAT NO EVOLUTION IS OCCURRING

  1. large population (no genetic drift)
  2. no mutations that affect gene pool
  3. mating b/w individuals in the population is random (no sexual selection)
  4. no migration of individuals in or out of population
  5. genes in population are all equally successful at reproducing
31
Q

Hardy-Weinberg equations

A

p + q = 1

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

32
Q

differential reproduction

A

when mutation/ recombination results in a favorable change then its more likely to pass on to the next generation (opposite is also true)

33
Q

inclusive fitness

A

measure of an organisms success in the population (based on number of offspring and ability of offspring to support others)— helping others of the same species- promotes idea that altruistic behavior can improve the fitness and success of a species as a whole.

34
Q

punctuated equilibrium

A

changes in some species occur in rapid bursts rather than evenly over time.

35
Q

stabilizing selection

A

selecting against extremes (regular bell-curve) - ex: human birth weight

36
Q

directional selection

A

adaptive pressure can lead to the emergence/ dominance of one extreme phenotype

37
Q

disruptive selection

A

two extreme phenotypes are selected over the norm

38
Q

adaptive radiation

A

rapid rise of a number of different species from a common ancestor. allows various species to occupy different niches, which decreases competition for limited resources

39
Q

speciation

A

formation of a new species through evolution

40
Q

pre and post-zygotic mechanisms resulting from reproductive isolation

A

pre- prevent formation of zygote

post- allow for gamete fusion but yield either nonviable or sterile offspring

41
Q

divergent evolution

A

two species with common ancestor become less similar b/c of different evolutionary pressures

42
Q

parallel evolution

A

two species with a common ancestor remain similar because of similar evolutionary pressures

43
Q

convergent evolution

A

two species with no recent common ancestor become more similar b/c of similar evolutionary pressures

44
Q

molecular clock model

A

degree of difference in the genome b/w two species is related to the amount of time since the two species broke off from a common ancestor