Q: In a family with six children, what is the probability that exactly four will be boys and two will be girls? Assume the probability of having a boy or girl is equal for each child.

$$P = \frac{6!}{4!2!} \times (0.5)^4$ \times (0.5)^2$ = 15 \times 0.0625 \times 0.25 = 0.234375$$

Q: Given a population in Hardy-Weinberg equilibrium with allele frequencies $$p = 0.7$$ and $$q = 0.3$$, what is the expected frequency of heterozygotes?

$$2pq = 2 \times 0.7 \times 0.3 = 0.42$$

Q: In a population, the frequency of a recessive disease is 1 in 10,000. Assuming Hardy-Weinberg equilibrium, what is the carrier frequency?

$$2pq = 2 \times 0.99 \times 0.01 = 0.0198$$

Question 1

A pedigree shows a trait that appears in every generation, affects both males and females equally, and is transmitted from affected fathers to both sons and daughters. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 2

In a family with six children, what is the probability that exactly four will be boys and two will be girls? Assume the probability of having a boy or girl is equal for each child.

Accepted Answer

$$P = \frac{6!}{4!2!} 	imes (0.5)^4$ 	imes (0.5)^2$ = 15 	imes 0.0625 	imes 0.25 = 0.234375$$

Question 3

A geneticist performs a chi-square test to compare observed and expected phenotypic ratios in a dihybrid cross. The observed counts are 90 round yellow, 30 round green, 30 wrinkled yellow, and 10 wrinkled green. What is the chi-square value for this data, assuming the expected ratio is 9:3:3:1?

Accepted Answer

$$\$$chi^2$$ = \sum \frac{(O - E)^2$}{E} = \frac{(90-84)^2$}{84} + \frac{(30-28)^2$}{28} + \frac{(30-28)^2$}{28} + \frac{(10-9)^2$}{9} = 0.429 + 0.143 + 0.143 + 0.111 = 0.826$$

Question 4

A woman with blood type AB and a man with blood type O have a child. What is the probability that their child will have blood type B?

Accepted Answer

$$P = 0.5$$

Question 5

In a three-point test cross, the following recombinant classes are observed: 10 double crossovers, 40 single crossovers between A and B, 30 single crossovers between B and C, and 120 parental types. What is the gene order?

Accepted Answer

The gene in the middle is C

Question 6

A plant species is tetraploid (4n). During meiosis, what is the expected consequence if univalents form instead of divalents?

Accepted Answer

Increased production of aneuploid gametes due to improper segregation

Question 7

A child is diagnosed with Prader-Willi syndrome, which is often caused by uniparental disomy of chromosome 15. Which PCR result would support this diagnosis?

Accepted Answer

Only maternal alleles are detected for chromosome 15 markers

Question 8

Which of the following best describes the effect of inversion heterozygosity on recombination?

Accepted Answer

Crossovers within the inverted region lead to unbalanced gametes

Question 9

Given a population in Hardy-Weinberg equilibrium with allele frequencies $$p = 0.7$$ and $$q = 0.3$$, what is the expected frequency of heterozygotes?

Accepted Answer

$$2pq = 2 	imes 0.7 	imes 0.3 = 0.42$$

Question 10

A forensic scientist uses CODIS data to calculate the probability that two unrelated individuals share the same genotype at a locus with allele frequencies $$p = 0.6$$ and $$q = 0.4. $$What is the match probability?

Accepted Answer

$$p^2$$ + $$q^2 = 0.36 + 0.16 = 0.52$

Question 11

In a population, the frequency of a recessive disease is 1 in 10,000. Assuming Hardy-Weinberg equilibrium, what is the carrier frequency?

Accepted Answer

$$2pq = 2 	imes 0.99 	imes 0.01 = 0.0198$$

Question 12

A population has the following genotype frequencies: $$AA = 0.36$$, $$Aa = 0.48$$, $$aa = 0.16. $$What is the inbreeding coefficient $$F$$?

Accepted Answer

$$F = 0$$

Question 13

A trait is determined by two additive alleles, $$A$$ and $$a$$, where each $$A$$ adds 2 units to the phenotype and each $$a$$ adds 1 unit. What is the expected phenotype for genotype $$Aa$$?

Accepted Answer

$$2 + 1 = 3$$

Question 14

In a reciprocal translocation heterozygote, which segregation pattern produces balanced gametes?

Accepted Answer

Alternate segregation

Question 15

A population has a phenotypic variance $$V_P = 20$$, genetic variance $$V_G = 8$$, and environmental variance $$V_E = 12. $$What is the heritability in the broad sense ($$H^2$$)?

Accepted Answer

$$H^2$$ = \frac{V_G}{V_P} = \frac{8}{20} = 0.4$$

Question 16

A mitochondrial disease is observed in a family. Only the children of affected mothers are affected, regardless of the father's genotype. What is the most likely explanation?

Accepted Answer

Maternal inheritance of mitochondrial DNA

Question 17

A population is under selection where the relative fitness of genotype $$AA is 1$$, $$Aa is 0.8$$, and $$aa is 0.6. If $$the initial frequency of $$A is 0.5$$, what will happen to the frequency of $$A$$ over time?

Accepted Answer

The frequency of $$A$$ will increase

Question 18

Which of the following best describes heteroplasmy in mitochondrial genetics?

Accepted Answer

Presence of more than one type of mitochondrial DNA within a cell

Question 19

A genome assembly has an N50 of 1 Mb and an L50 of 20. What does this mean?

Accepted Answer

50% of the genome is contained in 20 or fewer contigs, each at least 1 Mb in length

Comprehensive Genetics Study Guide: Key Concepts and Methods for Final Exam Preparation

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