Q: Which formula correctly calculates the map distance (in centimorgans, cM) between two genes based on recombination frequency?

$$d = \frac{\text{number of recombinant offspring}}{\text{total number of offspring}} \times 100$$

Q: In a population, the frequency of allele A is 0.7 and allele a is 0.3. According to Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes (Aa)?

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

Question 1

A geneticist observes a 9:7 phenotypic ratio in the F2 generation of a dihybrid cross in plants. Which type of gene interaction most likely explains this result?

Accepted Answer

Epistasis involving duplicate recessive genes

Question 2

In a biochemical pathway, gene A produces enzyme 1 and gene B produces enzyme 2. A mutation in gene A results in no product, regardless of the allele at gene B. What type of gene interaction is this?

Accepted Answer

Recessive epistasis

Question 3

A test cross between a dihybrid plant (AaBb) and a double recessive plant (aabb) yields the following offspring: 40 AaBb, 10 Aabb, 10 aaBb, 40 aabb. What is the most likely explanation for this result?

Accepted Answer

Partial linkage with recombination between A and B

Question 4

Which formula correctly calculates the map distance (in centimorgans, cM) between two genes based on recombination frequency?

Accepted Answer

$$d = \frac{	ext{number of recombinant offspring}}{	ext{total number of offspring}} 	imes 100$$

Question 5

During meiosis, crossing over occurs between homologous chromosomes. What is the primary genetic consequence of this process?

Accepted Answer

It increases genetic variation by producing new allele combinations

Question 6

A geneticist is mapping genes in humans using linkage analysis. Which of the following is required to calculate recombination frequency?

Accepted Answer

The number of recombinant and non-recombinant offspring

Question 7

Which equation represents the Hardy-Weinberg equilibrium for a gene with two alleles, A and a, with frequencies $$p$$ and $$q$$?

Accepted Answer

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

Question 8

In a population, the frequency of allele A is 0.7 and allele a is 0.3. According to Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes (Aa)?

Accepted Answer

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

Question 9

A researcher wants to test if a population is in Hardy-Weinberg equilibrium for a particular gene. Which statistical test should be used?

Accepted Answer

Chi-square test ($$\$$chi^2$$ test)

Question 10

Which of the following is a likely genetic consequence of inbreeding in a small population?

Accepted Answer

Increased frequency of homozygous genotypes

Question 11

A patient is found to have a mutation in a gene that results in a nonfunctional protein. Which of the following best describes the likely effect at the phenotypic level?

Accepted Answer

The patient may exhibit a disease or altered trait associated with loss of function

Question 12

Which of the following best describes balancing selection?

Accepted Answer

A type of selection that maintains multiple alleles in a population

Question 13

A genetic counselor is explaining the risk of a recessive genetic disorder to a couple. Both parents are carriers. What is the probability that their child will be affected?

Accepted Answer

$$\frac{1}{4}$$

Question 14

Which of the following is a real-world example of positive selection in humans?

Accepted Answer

Increased frequency of the sickle cell allele in malaria-endemic regions

Question 15

Which process is responsible for the exchange of genetic material between non-sister chromatids during meiosis?

Accepted Answer

Crossing over

Question 16

A bacterial strain is able to transfer antibiotic resistance to another strain through direct cell-to-cell contact. Which genetic exchange mechanism is responsible?

Accepted Answer

Conjugation

Question 17

Which of the following best explains why F- bacteria can become F+ after conjugation with an F+ donor?

Accepted Answer

The F plasmid is transferred from the F+ to the F- cell

Question 18

A geneticist uses data from bacterial conjugation experiments to map genes. Which observation indicates that two genes are close together on the chromosome?

Accepted Answer

They are transferred together at a high frequency

Question 19

Which of the following best describes the function of a plasmid in bacteria?

Accepted Answer

A small, circular DNA molecule that can carry genes for antibiotic resistance

Question 20

A newborn is tested for a genetic disorder using a PCR-based assay. Which of the following best explains the value of genetic testing in this scenario?

Accepted Answer

It allows for early diagnosis and potential intervention before symptoms appear

Genetics Exam II Study Guide: Gene Interaction, Linkage, Population Genetics, and Bacterial Genetics

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