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Final Flashcards

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Biology 101 flashcards
1
Q

Law of addition

A

use when events are mutually exclusive. Adds to 1

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2
Q

Law of multiplication

A

use when events are independent

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3
Q

when is binomial distribution used?

A

to calculate when a particular distribution of events will occur in a sample (ex. 3 out of 5 affected)

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4
Q

variables in a binomial distribution

A
  • P = probability of observing r incidences of type A events and n-r incidences of the other type(s)
  • n = the total number of events
  • r = the number of type A events of observed
  • q = the probability of type A event occurring
  • p = the probability of type A event not occurring (i.e. 1-q)
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5
Q

Hardy Weinburg Equilibrium

A

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

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6
Q

which variable do we use for disease incidence in Hardy Weinburg?

A

q^2

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7
Q

AR: given q^2, what is the carrier frequency in a population?

A

2pq, and we can usually assume p is 1. (same applies for estimating carrier frequency in females for an x-linked disease given the number of affected males)

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8
Q

AD Hardy Weinburg

A

we assume homozygotes are rare, so p~1. So, frequency of the mutant gene is equal to 1⁄2 the incidence of the trait

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9
Q

Assumptions of Hardy Weinburg

A

Population in infinitely large, mating is random, allele frequencies are constant over time

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10
Q

Subtypes of nonrandom mating

A

consanguinity, stratification, assortative mating

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11
Q

reminder: be able to describe second cousins once removed, etc.

A

abc

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12
Q

Coefficient of relationship definition

A

R: Relates to a consanguineous couple and indicates the proportion of alleles that on average they would be expected to share by virtue of their relationship.

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13
Q

Coefficient of relationship calculation

A

(1/2)^ number of people between, multiplied by 2 if related through two people (ex, mom and dad).

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14
Q

Coefficient of inbreeding definition

A

F: Relates to the child of a consanguineous relationship and indicates the probability that, at a given locus, the child will receive two identical alleles derived from a common ancestor. I think it’s 1/2R.

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15
Q

autozygous

A

homozygous for an allele inherited from same ancestral source (used for consanguinity usually)

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16
Q

Coefficient of inbreeding calculation

A

F = 1⁄2 R

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17
Q

mutation rate of a gene (μ)

A

q (frequency of allele in a population) represents a balance between the mutation rate of the gene (μ) and the effects of selection (s) against the allele
μ=q x s

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18
Q

Fitness (f)

A

probability of transmitting one’s genes to the next generation compared to average probability for the population.

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19
Q

Coefficient of selection (s)

A

1 - f (a measure of the loss of fitness)

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20
Q

how does medical treatment affect f for AD and AR conditions

A

f is increased in AD, non affected very much in AR

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21
Q

In general, what is value of mu?

A
  • μ = the mutation rate per gamete per generation

* ~10-5 to 10-6 per gene

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22
Q

what is risk for an AD condition in offspring on unaffected parents?

A

2μ (could arise in egg or sperm)

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23
Q

Prior probability that a female is a carrier of an X linked disorder is

A

4μ (many slides on this. Go through them)

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24
Q

directional selection

A

eliminates lethal dominant mutations, occasionally selects for a new mutation, pushes a population to homozygosity

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25
Q

Balancing selection

A

selection favoring heterozygotes, will maintain lethal recessive alleles, maintains/increases heterozygosity of population

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26
Q

Unstable selection

A

selection against heterozygotes, pushes population towards homozygosity, pushes populations to diverge

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27
Q

Genetic Drift

A

when the pool of gametes is formed for the next generation represents a random sample of alleles from the population (not representative of the population)

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28
Q

Founder Effect

A

when a small subpopulation breaks off from a larger population the allele frequencies may be different from those of the original population

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29
Q

Population Bottleneck

A

when a population is reduced to a very small number

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30
Q

LOF mutation

A

reduction or complete loss of protein function

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31
Q

GOF mutation

A

too much, too active, wrong time, wrong place, mutant protein gains a new function

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32
Q

Dominant negative mutation

A

nonfunctional mutant protein interferes with normal protein function

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33
Q

GOF associate with disease (homo/hetero)?

A

homogeneity

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34
Q

Which is more common- GOF or LOF?

A

LOF

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35
Q

Describe LOF in a recessive vs. dominant disease

A

In recessive, one LOF is fine because one working copy is enough. In dominant, LOF is not enough (haploinsufficiency)

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36
Q

Two hit hypothesis

A

dominant inheritance and recessive at cellular level

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37
Q

Mendelian condition

A

governed by single gene

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38
Q

Locus

A

A particular position on a chromosome

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39
Q

Allele

A

alternative variants of a DNA sequence

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40
Q

Polymorphism

A

the presence of two or more relatively common alleles in the population at a given locus

41
Q

Haplotype

A

a given set of alleles at a particular locus (or cluster of loci) on a single chromosome

42
Q

genotype

A

the set of alleles that make up a person’s genetic

constitution (collectively or at a single locus)

43
Q

phenotype

A

the observable expression of a genotype as a trait

morphological, clinical, cellular, biochemical, behavioral….

44
Q

— Genetic heterogeneity

A

Allelic heterogeneity and Locus Heterogeneity

45
Q

Locus Heterogeneity

A

where the same condition is caused by mutations at more than one loci (gene) *This can result in complementation in a recessive condition.

46
Q

Allelic heterogeneity

A

different mutations (alleles) within a given gene cause the same condition. Common when the condition is caused by loss-of-function mutations. Variation in the severity of the mutations can be related to prognosis.

47
Q

Phenotypic/clinical heterogeneity

A

different mutations in the same gene (different alleles) cause different conditions.

48
Q

Homozygote

A

An individual with a pair of identical alleles at a nuclear locus

49
Q

Heterozygote

A

An individual with two different alleles at a nuclear locus (usually one mutant/variant and one wildtype/reference, these individuals are often referred to as “carriers”)

50
Q

Compound heterozygote

A

An individual with two different mutant/variant/non-reference alleles of the same gene

51
Q

hemizygous

A

They only have one allele at a particular locus e.g. sex chromosomes in a male, deletion of one copy of a locus, Turner syndrome

52
Q

Law of segregation

A

When an individual produces gametes, the two copies (alleles) of a gene separate so that each gamete receives only one allele

53
Q

Law of independent assortment

A

The segregation of the alleles of one gene is independent of the segregation of the alleles of another gene (Note: this is only true if the genes are on different chromosomes or far apart on the same chromosome)

54
Q

Penetrance

A

The proportion of individuals with a particular genotype who manifest that genotype in their phenotype. The probability that a genotype will have ANY phenotypic expression.

55
Q

Expressivity

A

the degree to which a particular genotype is expressed in the phenotype

56
Q

True dominant

A

Heterozygote is indistinguishable from homozygote. (Rare/nonexistent? amongst human disorders. )

57
Q

Incomplete (semi) dominance

A

Homozygous individual has more severe phenotype than heterozygous individual.

58
Q

Co-dominance

A

Heterozygotes show phenotypic effects of both alleles equally e.g. AB blood group

59
Q

Can genes and alleles be dominant/recessive?

A

No, just phenotypes and inheritance patterns

60
Q

How does consanguinity complicate x-linked conditions?

A

can make it look like there is male to male transmission, can produce homozygous females

61
Q

anticipation

A

the tendency of a condition to become more severe (or have earlier onset) in successive generations

62
Q

Pleiotropy

A

when one gene influences two seemingly unrelated traits

63
Q

qualitative traits

A

dichotomous. discrete. Have it or don’t

64
Q

quantitative traits

A

variable. Can be measured

65
Q

sex-specific thresholds

A

If condition is less common in females, but a female has it, her relatives are MORE at risk than if she were a male with the condition

66
Q

How do you measure familial aggregation?

A

relative risk ratio of prevalence of disease in relatives to prevalence in general population

67
Q

Phenocopy

A

a mimic of a phenotype that is usually determined by a particular genotype produced instead by the interaction of environmental factors with a normal genotype e.g. breast cancer in a BRCA1/2 negative relative

68
Q

Genocopy

A

a genotype that causes a phenotype similar to that determined by a different genotype

69
Q

concordant

A

A pair of relatives who both have a certain trait are

70
Q

heritability definition

A

How much of the variation in phenotype between individuals in a population is caused by genetic differences. Heritability is not a fixed property of a trait. If environmental factors change, heritability may increase or decrease

71
Q

heritability calculation

A

Variance of a phenotype (VP) is determined by the sum of the individual causes of variation VP= VE+ VG.
Heritability is the proportion of total variance that is genetic h2=VG/VP

72
Q

when does homologous recombination occur?

A

prophase of meiosis I

73
Q

Do males or females have more crossover recombination?

A

females

74
Q

syntenic

A

loci are on same chromosome

75
Q

how many chromatids are involved in a crossover?

A

2, but can be several crossover events between different combinations of the chromatids

76
Q

Theta of 0 means

A

loci are so close we don’t see recombination between them

77
Q

Theta of 0.5 or 50% means

A

loci far enough away to assort independently or on different chromosomes

78
Q

Linkage

A

tendency for alleles close together on the same chromosome to be transmitted together

79
Q

Is linkage allele specific?

A

No, location specific

80
Q

Linkage equilibrium

A

The combinations of alleles are seen with the frequencies that you would predict from the individual allele frequencies in the population (multiply each allele frequency together to get expected genotype frequency)

81
Q

Reasons for linkage disequilibrium

A

allele entered population recently, loci are close together, loci relative to recombination hotspots, selection

82
Q

linkage analysis

A

Try to determine if gene of interest (location unknown) is is linked to particular marker with known location

83
Q

For an informative meiosis, one parent must be

A

heterozygous at both loci

84
Q

Positive LOD score

A

likely to be linked

85
Q

Negative LOD score

A

not likely to be linked

86
Q

LOD (Z) score between -2 and 3

A

inconclusive

87
Q

Association studies

A

population wide studies of alleles/haplotypes associated with phenotypes

88
Q

cohort studies

A

pick a population and divide by presence/absence of allele. See who develops condition

89
Q

case control studies

A

pick a group with condition, then pick matched controls. See you has allele/haplotype

90
Q

Risk (or incidence)

A

number of people who develop condition over total number of people (people in numerator also included in denominator)

91
Q

Odds

A

people who develop outcome over people who don’t (no one is in both numerator and denominator)

92
Q

What measure do we use in cohort studies?

A

relative risk (expresses probability)- risk of disease in those with a particular allele

93
Q

what measure do we use in case control studies?

A

odds ratio- odds of disease occurring in individuals with a particular allele over odds of disease occurring in individuals without the allele. “Having the allele give X times the odds of…” Compare to 1

94
Q

when does OD approximate RR?

A

When disease is rare, odds ratio approximates relative risk

95
Q

causes of association

A

causation, linkage disequilibrium, indirect effect, population stratification, type I error

96
Q

Bonferroni correction

A

adjusts threshold for total number of questions asked to maintain low false positive

97
Q

Interference

A

one crossover event reduces chance of another crossover event near by

98
Q

Yield of microarray for ID/DD/ASD/MCA

A

~15-30%

Human Genetics (2 decks)

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