Q: In a population where the mean inbreeding coefficient $$F = 0.0625$$, what is the expected frequency of heterozygotes at a locus with allele frequencies $$p = 0.7$$ and $$q = 0.3$$?

$$2pq(1-F) = 2 \times 0.7 \times 0.3 \times (1-0.0625) = 0.39375$$

Q: Which formula correctly gives the expected genotype frequencies under inbreeding for a locus with two alleles $$A$$ and $$a$$?

$$\begin{align*} \text{AA:} &\ p^2$ + pqF \\ \text{Aa:} &\ 2pq(1-F) \\ \text{aa:} &\ q^2$ + pqF \end{align*}$$

Q: A population has $$p = 0.9$$, $$q = 0.1$$, and $$F = 0.0625. $$What is the expected frequency of the $$aa$$ genotype?

$$q^2 + $$pqF = $$(0.1)^2 + 0.9$$ \times 0.1 \times 0.0625 = 0.01 + 0.005625 = 0.015625$$

Question 1

Which of the following best explains why the simple exponential model $$2^n$$ for the number of ancestors per generation leads to a paradox when extended far into the past?

Accepted Answer

It assumes that each ancestor is unique, which is not true due to inbreeding.

Question 2

In a population where the mean inbreeding coefficient $$F = 0.0625$$, what is the expected frequency of heterozygotes at a locus with allele frequencies $$p = 0.7$$ and $$q = 0.3$$?

Accepted Answer

$$2pq(1-F) = 2 	imes 0.7 	imes 0.3 	imes (1-0.0625) = 0.39375$$

Question 3

Which of the following statements about inbreeding is CORRECT?

Accepted Answer

Inbreeding increases the frequency of homozygotes and decreases the frequency of heterozygotes.

Question 4

A child is the product of a double first cousin mating. What is the inbreeding coefficient $$F$$ for this child?

Accepted Answer

$$F = \frac{1}{8} = 0.125$$

Question 5

If a population has a high inbreeding coefficient primarily due to a small population size and not due to cultural preference for consanguineous marriage, which component of inbreeding is most responsible?

Accepted Answer

Random inbreeding ($$F_r)$$

Question 6

Given a genealogy where an individual’s parents are both first cousins and second cousins, how would you calculate the total inbreeding coefficient $$F$$ for their child?

Accepted Answer

Sum $$\left(\frac{1}{2}\right)^i$$ for each loop through a common ancestor, where $$i is $$the number of individuals in the loop (excluding the child).

Question 7

Which formula correctly gives the expected genotype frequencies under inbreeding for a locus with two alleles $$A$$ and $$a$$?

Accepted Answer

$$\begin{align*} 	ext{AA:} &\ p^2$ + pqF \ 	ext{Aa:} &\ 2pq(1-F) \ 	ext{aa:} &\ q^2$ + pqF \end{align*}$$

Question 8

In a population, the observed frequency of isonymous marriages is $$P = 0.12. $$Using the Crow and Mange method, what is the estimated mean inbreeding coefficient $$F$$?

Accepted Answer

$$F = \frac{P}{4} = \frac{0.12}{4} = 0.03$$

Question 9

Why does inbreeding increase the prevalence of rare recessive genetic disorders in human populations?

Accepted Answer

Because inbreeding increases the frequency of homozygotes, making it more likely for rare recessive alleles to be expressed.

Question 10

A population has $$p = 0.9$$, $$q = 0.1$$, and $$F = 0.0625. $$What is the expected frequency of the $$aa$$ genotype?

Accepted Answer

$$q^2 + $$pqF = $$(0.1)^2 + 0.9$$ 	imes 0.1 	imes 0.0625 = 0.01 + 0.005625 = 0.015625$$

Question 11

If a common ancestor in a genealogical loop is themselves inbred with $$F_A = 0.125$$, how does this affect the inbreeding coefficient $$F$$ for a descendant, and what formula should be used?

Accepted Answer

$$F = \sum \left(\frac{1}{2}\right)^i (1 + F_A)$$, where $$i is $$the number of individuals in the loop and $$F_A is $$the inbreeding coefficient of the common ancestor.

Question 12

Which of the following is a real-world example of how cultural practices can influence genetic variation through inbreeding?

Accepted Answer

Some Muslim populations have a preference for certain types of first cousin marriage, affecting the frequency of consanguineous unions.

Question 13

In a population, the observed probability of isonymous marriages is $$P = 0.15$$ and the expected probability under random mating is $$P_r = 0.12. $$What is the nonrandom component of inbreeding $$F_n$$ using the formula $$F_n = \frac{P - P_r}{4(1 - P_r)}$$?

Accepted Answer

$$F_n = \frac{0.15 - 0.12}{4(1 - 0.12)} = \frac{0.03}{4 	imes 0.88} = \frac{0.03}{3.52} \approx 0.0085$$

Question 14

Which of the following best describes the difference between identity by descent and identity by state?

Accepted Answer

Identity by descent means two alleles are identical because they were inherited from a common ancestor; identity by state means they are identical in sequence but not necessarily by ancestry.

Question 15

A rare recessive allele has frequency $$q = 0.01 in a $$population. What is the expected frequency of affected individuals (homozygous recessive) under Hardy–Weinberg equilibrium and under first cousin mating ($$F = 0.0625$$)?

Accepted Answer

Hardy–Weinberg: $$q^2 = 0.0001$; First cousin mating: q^2$ + Fpq = 0.0001 + 0.0625 	imes 0.01 	imes 0.99 = 0.0001 + 0.00061875 = 0.00071875$$

Question 16

Which of the following scenarios would most likely result in a negative nonrandom inbreeding component ($$F_n \u003c 0) in a $$population?

Accepted Answer

A cultural taboo against cousin marriage, leading to avoidance of consanguineous unions.

Question 17

Which of the following is NOT a limitation of using surname isonymy to estimate inbreeding coefficients in human populations?

Accepted Answer

It provides direct genetic evidence of allele sharing.

Question 18

In a population, the mean inbreeding coefficient is $$F = 0.0115. $$Which of the following best describes the genetic impact of this level of inbreeding?

Accepted Answer

It is similar to the effect of all marriages being between second cousins.

Inbreeding: Quantification, Genetic Impact, and Population Analysis

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