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MCAT > Biology Ch 12. Genetics and Evolution > Flashcards

Biology Ch 12. Genetics and Evolution Flashcards

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1
Q

Chromosomes

A

Contain genes in a linear sequence

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2
Q

Genes

A

Genetic sequences that code for heritable traits that can be passed from one generation to the next, organized in a linear sequence into chromosomes

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3
Q

Alleles

A

The alternative forms of a gene

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4
Q

Dominant allele

A

Requires only one copy to be expressed

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5
Q

Recessive allele

A

Requires two copies to be expressed

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6
Q

Genotype

A

The combination of alleles one has at a given genetic locus

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7
Q

Locus

A

Location on a specific chromosome for each gene, consistent among human beings

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8
Q

Homozygous

A

Having two of the same allele

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9
Q

Heterozygous

A

Having two different alleles

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10
Q

Hemizygous

A

Having only one allele, ex. the male sex chromosome

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11
Q

Phenotype

A

The observable manifestation of a genotype

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12
Q

Complete dominance

A

When the effect of one allele completely masks the effect of another

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13
Q

Codominance

A

When more than one dominant allele is present

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14
Q

Incomplete dominance

A

No dominant alleles, heterozygotes express a phenotype that is intermediate between the two homozygous genotypes

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15
Q

Penetrance

A

The proportion of a population carrying the allele who actually express the phenotype, or the probability that, given a particular genotype, a person will express the phenotype

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16
Q

Expressivity

A

The varying phenotypic manifestations of a given genotype

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17
Q

Mendels first law (of segregation)

A

States than an organism has two alleles for each gene, which segregate during meiosis, resulting in gametes carrying only one allele for a trait

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18
Q

Mendels laws

A

Help explain the inheritance of genes from parent to offspring

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19
Q

Mendels second law (of independent assortment)

A

States that the inheritance of one allele does not influence the probability of inheriting an allele for a different trait

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20
Q

The Griffith Experiment

A

Demonstrated the transforming principle, converting non-virulent live bacteria into virulent bacteria by exposure to heat-killed virulent bacteria

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21
Q

The Avery-MacLeod-McCarty experiment

A

Demonstrated that DNA is the genetic material because degradation of DNA led to a cessation of bacterial transformation

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22
Q

The Hershey-Chase experiment

A

Confirmed that DNA is the genetic material because only radio labeled DNA could be found in bacteriophage-infected bacteria

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23
Q

Full penetrance

A

Individuals with more than 40 sequence repeats, all individuals with their allele show symptoms of Huntington’s disease

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24
Q

Constant expressivity

A

All individuals with a given genotype express the same phenotype

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25
Q

Variable expressivity

A

Individuals with the same genotype may have different phenotypes

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26
Q

Recombination

A

Small segments of genetic material are swapped between chromatids in homologous chromosomes, resulting in novel combinations of alleles that were not present in the original chromosome, allows for the inheritance of one gene to be independent of the inheritance of all others, complicated by discovery of linked genes

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27
Q

Gene pool

A

All of the alleles that exist within a species

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28
Q

Mutations

A

Changes in the DNA sequence

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29
Q

Nucleotide mutations

A

Point mutations and frameshift mutations

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30
Q

Point mutations

A

The substituting of one nucleotide for another

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31
Q

Frameshift mutation

A

Moving the three-letter transcriptional reading frame

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32
Q

Silent mutation

A

No effect on the protein, typically because wobble in genetic code

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33
Q

Missense mutation

A

Results in the substitution of one amino acid for another

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34
Q

Nonsense mutation

A

Results in the substitution of a stop codon for an amino acid

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35
Q

Insertions and deletions

A

Result in a shift in the reading frame, leads to changes for all downstream amino acids

36
Q

Chromosomal mutations

A

Include larger-scale mutations affecting whole segments of DNA

37
Q

Deletion mutations

A

Occur when a large segment of DNA is lost

38
Q

Duplication mutations

A

Occur when a segment of DNA is copied multiple times

39
Q

Inversion mutations

A

Occur when a segment of DNA is reversed

40
Q

Insertion mutations

A

Occur when a segment of DNA is moved from one chromosome to another

41
Q

Translocation mutations

A

Occur when a segment of DNA is swapped with a segment of DNA from another chromosome

42
Q

Genetic leakage

A

A flow of genes between species through hybrid offspring

43
Q

Genetic drift

A

Occurs when a composition of the gene pool changes as a result of chance

44
Q

Founder effect

A

Results from bottlenecks that suddenly isolate a small population, leading to inbreeding and increased prevalence of certain homozygous genotypes

45
Q

Wild type allele

A

Alleles that are considered “normal” or “natural”

46
Q

Mutagens

A

Substances that cause mutations

47
Q

Transposons

A

Can insert and remove themselves from the genome, will disrupt gene if inserted into middle of a coding sequence

48
Q

Inborn error of metabolism

A

Class of deleterious mutations that result in defects in genes required for metabolism

49
Q

Things that result in decreased genetic diversity

A

Genetic drift, founder effect, inbreeding, may reduce fitness of population

50
Q

Inbreeding depression

A

Loss of genetic variation that results in decreased fitness

51
Q

Outbreeding/Outcrossing

A

The introduction of unrelated individuals into a breeding group

52
Q

Punnett squares

A

Visually represent the crossing of gametes from parents to show relative genotypic and phenotypic frequencies

53
Q

Parent generation

A

Represented by P in punnett square

54
Q

Filial generations

A

Offspring generations, represented by F1, F2… in punnett square

55
Q

Monohybrid cross

A

Accounts for one gene

56
Q

Dihybrid cross

A

Accounts for two genes

57
Q

Sex-linked traits

A

Traits on the X chromosome that are more common in men because they only have one copy of the X chromosome so one recessive allele means they have the trait

58
Q

Recombination frequency

A

The likelihood that two alleles being separated during crossing over in meiosis, proportional to the distance between the genes on the chromosome

59
Q

Genetic maps

A

Can be made using recombination frequency, scale in centimorgans, 1 centimorgan = 1 % chance of recombination

60
Q

Hardy-Weinberg Principle

A

States that if a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant

Criteria:
Population large
No mutations that affect gene pool 
Mating is random
No migration of individuals
Genes are equally successful at being reproduced
61
Q

Allele frequency

A

How often an allele appears in a population

62
Q

Hardy-Weinberg Equilibrium

A

When allele frequencies remain constant in a population

63
Q

Biometric techniques

A

Quantitative approaches to biological data

64
Q

Test cross

A

Crossing an organism of an unknown genotype with a organism that is homozygous recessive to determine the unknown genotype

65
Q

Hardy Weinberg equations

A 
p - freq of dominant allele
q - freq of recessive allele
p^2 - freq of homozygous dom
2pq - freq of heterozygous
q^2 - freq of homozygous recessive

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

66
Q

Natural selection

A

States that chance variations exist between individuals and that advantageous variations afford the most opportunities for reproductive success and will thus pass those variations on to their offspring

67
Q

Advantageous variations

A

Those that increase an individuals fitness for survival or adaption to the environment

68
Q

Modern synthesis model

A

neo-Darwinism - accounts for mutation and recombination as mechanisms of variation and considers differential reproduction to be the mechanism for reproductive success

69
Q

Differential reproduction

A

When a mutation or recombination that is favorable occurs, that chance will more likely pass on to the next generation and it will become more common

70
Q

Inclusive fitness

A

Considers an organisms success to be based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others, survival of offspring or relatives ensues appearance of genes in subsequent generations, promotes the idea that altruism can improve the fitness and success of a species as a whole

71
Q

Punctuated equilibrium

A

Considers evolution to be a very slow process with intermittent rapid bursts of evolutionary activity

72
Q

Stabilizing selection

A

Keeps phenotypes in a narrow range, excluding extremes

73
Q

Directional selection

A

Moves the average phenotype toward one extreme

74
Q

Disruptive selection

A

Moves the population toward two different phenotypes at the extremes and can lead to speciation, reason for polymorphisms

75
Q

Speciation

A

The formation of new species through evolution

76
Q

Adaptive radiation

A

The rapid emergence of multiple species from a common ancestor, each of which occupies its own ecological niche

77
Q

Species

A

The larges group of organisms capable of breeding to form fertile offspring, reproductively isolated from each other by pre or post zygotic mechanisms

78
Q

Reproductively isolated

A

Once evolution has lead to enough changes that these populations could no longer freely interbreed

79
Q

Prezygotic mechanisms

A

Prevent formation of the zygote completely, includes temporal isolation, ecological isolation, behavioral isolation, reproductive isolation, and gametic isolation

80
Q

Postzygotic mechanisms

A

Prevents reproductive success after the zygote is formed, includes hybrid inviability, hybrid sterility, and hybrid breakdown

81
Q

Divergent evolution

A

Occurs when two species sharing a common ancestor become more different

82
Q

Parallel evolution

A

Occur when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures

83
Q

Convergent evolution

A

Occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures

84
Q

Molecular clock model

A

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

85
Q

Fitness

A

Level of reproductive success, directly related to the relative genetic contribution of this individual to the next generation

86
Q

Polymorphisms

A

Naturally occurring differences in form between members of the same population, such as light and dark coloration in the name species of butterfly

87
Q

Niche

A

A specific environment, including habitat, available resources, and predators for which a species is specifically adapted

MCAT (67 decks)

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