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Biochemistry > Exam #5: Population Genetics > Flashcards

Exam #5: Population Genetics Flashcards

1
Q

Polymorphism

A

Different forms of a gene in at least 1% of the population

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2
Q

Example of a highly polymorphic gene

A

HLA (Human Leukocyte Antigen) & cytochrome p450

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3
Q

Example of a non-polymorphic gene

A

Histones

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4
Q

How many deleterious recessive mutations does the average person carry?

A

3

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5
Q

How many nucleotide polymorphisms are there between unrelated humans?

A

Approximately 6 million, which works out to 1/1,000 base pairs

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6
Q

Describe polymorphisms in the context of race.

A
  • 90% of genetic variation can be found within populations considered a race
  • Only 10% of that variation is unique to the race
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7
Q

What are the four characteristics of an ideal population?

A

1) Large population size
2) Equal fitness of offspring (ability to reproduce)
3) Random mating
4) No influx or new alleles by migration or mutation

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8
Q

What did Hardy & Weinberg derive in their formula?

A

Proof that in ideal populations allele frequencies do not change over time

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9
Q

What are the four disturbances that can occur in the Hardy Weinberg equilibrium?

A

1) Genetic Drift (population is small)
2) Selection (fitness of offspring is unequal)
3) Assortative mating (mating is nonrandom)
4) Population bottlenecks & founder effect

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10
Q

Which of the four disturbances in the Hardy Weinberg equilibrium will NOT change the expected allele frequency over time; rather, the expected ratio of homozygosity & heterozygosity?

A

Non-random (assortative) mating will increase the frequency of homozygosity

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11
Q

f(a)

A

mutant

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12
Q

f(A)

A

wild-type

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13
Q

aa & AA=

A

f(a)^2 or f(A)^2

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14
Q

f(a) & f(A) heterozygotes

A

2*f(a)xf(A)

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15
Q

Carrier frequency in recessive diseases

A

2 x square root of prevalence

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16
Q

Allele frequency in x-linked recessive diseases

A

Fraction of males that are affected

17
Q

Genetic Drift

A
  • Statistical variation that can lead to the disappearance or multiplication of rare alleles
  • Consequence of small population size?
18
Q

Selection

A
  • Over time will reduce the number of mutant alleles in a population
  • HOWEVER, at some point the frequency of mutant alleles will stabilize at a low level
  • Loss of mutant alleles will equal the appearance of spontaneous mutations, resulting in equilibrium
19
Q

Heterozygote Advantage

A

Being heterozygous for a mutant allele confers some selective advantage (protection against something else)

20
Q

CFTR Heterozygote Advantage

A

Protection from Typhoid Fever

21
Q

Hemoglobin B/ Sickle Cell Anemia Heterozygote Advantage

A

Protection from Malaria

22
Q

Hemoglobin B/ Beta- Thalassemia Heterozygote Advantage

A

Protection from Malaria

23
Q

HFE/ Hemochromatosis Heterozygote Advantage

A

Protection from Plague

24
Q

Assortative Mating

A
  • Non-random mating

- Selection of partners based on a specific genetic trait

25
Q

What effect does the mating of genetically similar individuals have?

A

Increases the degree of homozygosity in a population beyond what is predicted

26
Q

In a first cousin marriage, what is the risk of having a child with a genetic disease?

A

5%, 2% above the risk to the general population

27
Q

Founder Effect

A
  • Population is wiped out by a catastrophic event

- Population has to recover from a small founder population, which can amplify rare alleles

28
Q

Ellis van Creveld Syndrome

A
  • Caused by a mutation in the EVC gene
  • Example of the founder effect in Older Amish of Lancaster County, PA
  • Symptoms include: shortening of limbs, postaxial polydactyly & heart defects
29
Q

Ashkenazi Jews

A

Tay-Sachs Disease

30
Q

French Canadians (Quebec)

A

Tyrosinemia

31
Q

GWAS

A
  • Genome wide association study

- millions of single nucleotide polymorphisms (SNPs) are analyzed

32
Q

Odds Ratio

A
  • Describes the strength of association between a SNP & disease
  • NOTE, SNPs are not necessarily disease causing; rather, they lie outside coding regions that are and show linkage with the mutation that contributes to the disease
33
Q

Why are young, genetically isolated populations the key to success for association studies?

A

Linkage disequilibrium between a disease trait & genetic markers scattered all over the genome

Biochemistry (17 decks)

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