Multifactorial Inheritance

Question 1

Population Genetics

Answer 1

Study of distribution of genes in populations, central to human genetics (genetic counseling)

Question 2

Hardy-Weinberg Probability Analysis

Answer 2

Used in for population genetics studies, assumes ideal conditions

Question 3

Hardy-Weinberg Equations

Answer 3

Where p = A and q = a

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

Question 4

Calculating Probability

Answer 4

Product of two independent events occurring separately

Question 5

Hardy-Weinberg Conditions

Answer 5

1. Large population
2. Randomly mating population
3. No selection
4. No mutations
5. No migrations

Question 6

Hardy-Weinberg Calculation Algorithm

Answer 6

1. Breakdown allele frequency into decimals
2. Use decimal value to determine individual allele value
3. Evaluate individual allele value using p+q=1
4. Evaluate desired combination (AA, Aa, aa)

Question 7

General Rule for Human Population Genetics

Answer 7

Heterozygotes of a rare recessive abnormality are rather common.

Carriers appear more frequently than homozygous recessive.

Question 8

Sickle Cell Anemia

Answer 8

Homozygote frequency = 1 : 500

Heterozygote frequency = 1 : 10

Question 9

PKU

Answer 9

Homozygote frequency: 1 : 25000

Heterozygote frequency: 1 : 80

Question 10

Consanguinity Consequences

Answer 10

Share more of the same alleles than individuals from population at large, could be good or bad alleles

Question 11

Tay-Sach’s Disease

Answer 11

Lysosomal Disorder

Question 12

Multifactorial Inheritance

Answer 12

Disorders are the result of inherited genes and interaction with the environment

Question 13

Polygenic inheritance

Answer 13

Additive effect of a gene contributes to phenotype, more A/B genes = increased height

If alleles are distributed equally in population, then normal distribution should be expected

Question 14

Examples of multifactorial diseases

Answer 14

Diabetes, hypertension, obesity

Question 15

Risk Genes

Answer 15

Additive effect of risk genes places higher propensity to acquire disorder or disease

Question 16

Threshold level model of multifactorial inheritance

Answer 16

Point where enough risk traits are acquired and disorder will emerge

Question 17

Threshold and Liability

Answer 17

Liability is genetic predisposition to a disease and environmental influences

Question 18

Sex differences in multifactorial inheritance disorders

Answer 18

Some disorders favor one gender over the other, need less risk genes to show the disease or need more risk genes to show the disease

Females more prone to anencephaly and spina bifida
Males more prone to pyloric stenosis

Question 19

Affected couples who have children

Answer 19

Likely to transmit greater # of risk genes to children, children more prone to acquiring disorder

Question 20

General rule of gender inheritance of multifactorial traits

Answer 20

Less frequently affected sex will transmit condition more often to the opposite sex

Least affected gender has a higher risk threshold

Question 21

Genetic Variation Changes

Answer 21

Changes in frequency of alleles due to:

1. Random genetic drift
2. Founder effect
3. Selection
4. Stable polymorphism

Question 22

Albinism Frequency

Answer 22

1 : 8 Hopi Indians
1 : 200 among Cuna Indians
1 : 20,000 in European Caucasians

Question 23

Sickle Cell Disease Frequency

Answer 23

1 : 25 in Africans

1 : 500 in African Americans