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BIOL 202 > Midterm > Flashcards

Midterm Flashcards

1
Q

Law of Equal Segregation

A

During production of gametes, each allele gets equally partitioned between egg/sperm.

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2
Q

Law of Independent Assortment

A

Alleles on different chromosomes assort independently at meiosis

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3
Q

Exceptions to Law of Equal Segregation

A

Complex Traits

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4
Q

Exceptions to Law of Independent Assortment

A

Linked Genes, Alleles far apart on same chromosomes

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5
Q

Prophase

A
  • DNA condenses

- spindle forms

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6
Q

Prometaphase

A
  • nuclear envelope disintegrates

- some microtubules bind to kinetochors

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7
Q

Metaphase

A
  • chromosomes line up on metaphase plate
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8
Q

Anaphase

A
  • sister chromatids get pulled back
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9
Q

Telophase

A
  • nucleus reforms
  • cleavage furrow forms
  • cytokenesis
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10
Q

Cross-over happens when?

A

Prophase 1

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11
Q

When does independent assortment happen?

A

Metaphase 1

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12
Q

Bivalent

A

pair of synapsed dyads

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13
Q

Dyad

A

pair of sister chromatids

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14
Q

Tetrad

A

four chromatids making up bivalent

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15
Q

Consanguinity

A

incest

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16
Q

Dominant Trait Pedigree Analysis

A
  • seen every generation
  • affected offspring => affected parents
  • 50% of heterozygote children are affected
  • unaffected does not transmit trait
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17
Q

Recessive Trait Pedigree Analysis

A
  • skips generations

- 25% of heterozygote children affected

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18
Q

SRY Gene

A

gene on Y chromosome determining male characteristics

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19
Q

pseudoautosomal regions

A

homologous regions on both X and Y chromosomes (near telomeres) allowing pairing in meiosis

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20
Q

sex determination in mammals vs Drosophila

A

Mammals: determined by having Y chromosome
Drosophila: determined by ratio of X chromosomes

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21
Q

Kleinfelter syndrome

A

XXY (male)

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22
Q

Turner Syndrome

A

X0 (female)

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23
Q

Gene Dosage in humans vs Drosophila

A

Mammals: X chromosome disactivation during embryogenesis
Drosophila: single X chromosome gene is hyperactivated

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24
Q

X Linked Recessive Pedigree Analysis

A
  • usually males affected
  • affected sons usually born from carrier mothers
  • skips generations
  • 50% of sons of heterozygous mothers are affected
  • never passed from father to son (zig-zag inheritance)
  • all daughters of affected fathers are carriers
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25
Q

Loss of function mutant allele

A
  • aka null allele

- produces protein which is non-functional

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26
Q

Haplo-sufficiency

A
  • one functional copy is enough to produce phenotype

- mutation is recessive

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27
Q

Haplo-insufficiency

A
  • one functional copy is not enough to produce phenotype

- mutation is dominant

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28
Q

Dominant negative

A
  • mutation that impedes the nonmutant protein
  • usually seen in dimers
  • effect is that mutation is dominant
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29
Q

Gain of function mutant allele

A
  • aka hyperactive

- produces protein which has much greater effect than non-mutant allele

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30
Q

Incomplete Dominance

A
  • type of haplo-insufficiency

- intermediate phenotype in heterozygotes

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31
Q

Codominance

A
  • heterozygotes have two different simultaneous traits
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32
Q

Allelic series

A
  • more than 2 alleles

- can have complex dominance relationship

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33
Q

Pleiotropy

A
  • gene affecting multiple traits

- can be upstream of many processes

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34
Q

Recessive lethal

A

Dies before being able to reproduce, or in utero

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35
Q

Penetrance

A

presence or absence of phenotype

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36
Q

Expressivity

A

strength or variability of phenotype

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37
Q

Gene Modifiers

A

genes that affect expressivity or penetrance of another gene

38
Q

Genetic Dissection

A

Using mutants to investigate biological processes

39
Q

Genetic Screen

A

Looking through natural or mutagenized population to identify mutant phenotypes

40
Q

Mutant Analysis Overview

A
  1. dominant or recessive?
    • check phenotype of F1 of two inbred lines
  2. how many genes are affected in each mutant?
    • check distribution of F2 phenotypes (ex: 3:1, 9:3:3:1)
  3. how many genes have I isolated in my screen?
    • complementation test
  4. how do the genes interact with each-other to give wild type?
    • double mutant analysis
41
Q

Complementation Test

A

test for allelism

  • mutant x mutant
  • mutant phenotype => same gene (alleles of each-other)
  • wild type phenotype => different gene
42
Q

Complementation Group

A
  • contains mutants that don’t complement each-other

- group === alleles of a particular gene

43
Q

Double Mutant Analysis

A
  • analyses interaction between two genes
  • look at F1 x F1 = F2 cross from complementation test
    Possibilities:
  • Additive: 9:3:3:1
  • Complementarity: 9:7
  • Epistasis (dominant): 12:3:1
  • Epistasis (recessive): 9:3:4
44
Q

Additive Gene Action

A

Genes working independently on same trait (9:3:3:1 on F2)

45
Q

Complementary Gene Action

A

Need both genes to get trait (9:7 ratio)

46
Q

Epistasis

A

A mutation masks another (double mutant looks same as one other)

  • Recessive (9:3:4)
  • Dominant (12:3:1)
47
Q

Possible Complementary Gene Action Mechanisms

A

Linear pathway, Parallel Pathway, Regulatory Pathway

48
Q

Recombination

A

Production of new combination of alleles of different genes by meiosis

49
Q

Independent Assortment meaning for recombination

A

Same amount of parental and recombinant gametes

50
Q

Degree of Linkage

A
  • when genes are close together on same chromosome, parental alleles tend to stay together
  • consequence is more parental gametes (skewed 9:3:3:1 ratio)
51
Q

Prophase 1 Recombination

A

Pairs of homologous chromosomes synapse, causing crossing-over events
- only way to get recombinant gametes for genes on same chromosome

52
Q

Evaluating Degree of Linkage

A

Test Cross AB/ab x ab/ab

- calculate recombinant frequency (RF)

53
Q

Recombinant Frequency

A 
# recombinants / # total offspring
RF of 50% is unlinked, <50% is linked
54
Q

Gene Mapping Units

A

cM (centimorgans) or m.u. (map units)

- proportional but not equal to physical distance

55
Q

Population Genetics

A

Studying why populations:

  • differ (allele frequency)
  • change over time
56
Q

Forces affecting Populations

A
  • mutations
  • selection
  • migration
  • genetic drift
57
Q

Types of Genetic Variation

A
  • SNP
  • indel (insert, delete)
  • microsatellite (# repeats)
58
Q

Haplotype

A

DNA sequence for section of chromosome

  • used to classify
  • can be organized phylogenetically
59
Q

Genotype Pool

A

frequency of genotypes of an allele

60
Q

Gamete Pool

A

frequency of an individual allele

61
Q

Calculating allele frequency

A 
p = Fmm + 1/2Fmn
q = Fnn + 1/2Fmn
62
Q

Hardy-Weinberg Conditions

A 
random mating
no selection
no migration
no mutation
infinitely large population
63
Q

Hardy-Weinberg Proportions

A 
Freq(AA) = p^2
Freq(Aa) = 2pq
Freq(aa) = q^2
64
Q

Hardy-Weinberg Theory

A

When HW conditions hold, allele frequency stays the same after X generations

65
Q

Inbreeding Consequences

A

increases frequency of homozygotes
lowering of population’s fitness
increase change of inheriting recessive disorders

66
Q

HW Proportions with Inbreeding

A 
Freq(AA) = p^2 + pqF
Freq(Aa) = 2pq(1 - F)
Freq(aa) = q^2 + pqF
67
Q

Inbreeding Coefficient

A

probability that two alleles inherited by an individual are identical by descent

F = (1/2)^2 (1 + Fa)
(assumption is full sib mating, for half sib, divide by two)
Fa is prob that ancestor is identical by descent

68
Q

Inbreeding Depression Factor

A

Increased chance of inheriting a recessive disorder

(q^2 + pqF)/q^2

69
Q

Mutation Rate in Population

A

very slow

10^9 mutation/bp/generation in humans, much higher if whole gene is considered

70
Q

Genetic Drift

A

When population is small or fragmented (population bottleneck), random chance causing drastic loss of genetic variation in a population

71
Q

Population Bottleneck

A

Quick reduction or fragmentation of population

72
Q

Probability of allele fixation

A

P^(2N)

73
Q

Natural Selection

A
  • Directional shift in allele frequency due to environment conditions
  • Can be rapid
  • Works by favouring higher relative fitness
74
Q

Relative Fitness

A

fitness compared to max absolute fitness

75
Q

Selection Coefficient

A

aka “s”

difference between relative fitness and 1

76
Q

Balancing Selection

A

Happens when heterozygotes are favoured
- consequence is balancing of alleles until equilibrium

WAA = 1 - s1
WAa = 1
Waa = 1 - s2
Freq(AA) = s1 / (s1 + s2)
77
Q

Balancing Mutation Rate against Natural Selection

A

u = mutation rate
q^2 = u/s
(q at equilibrium)

78
Q

Multifactorial Hypothesis Conditions

A

Complex traits caused by:

  • several loci
  • no dominance effects
  • how environment reacts with genotype
79
Q

Meristic Trait

A

based on a count of something (hairs, bristles)

80
Q

Threshold Trait

A

how liable you are to develop a certain disease/condition

81
Q

Statistical Formulas

A

Mean = 1/n (Sum of Xs)
Variance, Vx = 1/n (Sum of Xs - X)^2
Covariance, COVxy = 1/n (Sum of (Xi - X)(Yi - Y))
Correlation, Rxy = COVxy = Sqrt(VxVy)

82
Q

Multifactorial Hypothesis Formulas

A 
Xi = Mean(X) + g + e 
g = genetic deviation
e = environmental deviation

Vx = Vg + Ve

83
Q

Multifactorial Model

A
  1. Make two inbred lines
  2. Calculation variation in two lines (Ve)
  3. Make F2 generation
  4. Calculation variation of F2 (Vx)
84
Q

Broad Sense Heritability

A

Proportion of phenotype variability due to genetics
Value depends on the experimental setup (inbred lines, environments chosen, etc)

H^2 = Vg/Vx (0 to 1, dimensionless)

85
Q

Twin Studies

A

Used to get heritability estimates for humans
Need to separate at birth
Calculate correlation between traits:

H^2 = COVx’x’’ / Vx

86
Q

Narrow Sense Heritability

A

Measure of degree which an individual’s genetics determines phenotype of offspring (additive effects)

Vg = Va + Vd
h^2 = Va / Vx
87
Q

Breeder’s Equation

A

Do selection experiment
S = difference between population and selection means
R = difference between old and new populations

h^2 = R / S

88
Q

QLT Mapping

A

Using genetic markers to find QLTs in genome
- ex: SNPs, minisatellites, other known loci

  1. start with two inbred lines (P1, P2)
  2. make F1 hybrid line
  3. background F1 with P1 (BC1)
  4. examine BC1 trait and market phenotypes

Compare trait values across recombinant classes, find correlation between markers and traits

89
Q

Lod score

A

Higher means better likelihood of nearby QTL

90
Q

Genome-Wide Association Studies

A

GWAS

Using data from large populations to find QTLs, relying on natural meiosis

BIOL 202 (1 decks)

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