Question 1

During meiosis, homologous chromosomes separate during which phase, and what is the consequence if this process fails (nondisjunction) in humans?

Accepted Answer

Anaphase I; results in gametes with abnormal chromosome numbers such as Down syndrome

Question 2

A woman is heterozygous for a short sequence repeat (SSR) at a single locus on her X chromosome. If PCR is performed on her DNA for this locus, how many bands would you expect to see on a gel, and why?

Accepted Answer

Two bands, because she has two different SSR alleles on her X chromosomes

Question 3

If two genes are linked and the recombination frequency ($$rf) $$between them is 10%, what proportion of the offspring from a test cross would you expect to be recombinant types?

Accepted Answer

$$10\%$$

Question 4

Huntington’s disease is caused by which of the following genetic mechanisms?

Accepted Answer

A dominant gain-of-function mutation due to CAG repeat expansion

Question 5

Cancer is often described as a genetic disease. Which statement best explains why?

Accepted Answer

Cancer arises from mutations in genes that control cell growth and division

Question 6

What is the probability that a couple with three children will have all boys, assuming the probability of having a boy is $$0.5$$ for each child?

Accepted Answer

$$0.125$$

Question 7

Which histone modification is most commonly associated with increased transcriptional activity?

Accepted Answer

Histone acetylation

Question 8

A pedigree shows a disease that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 9

Which of the following best describes the function of restriction enzymes in molecular biology?

Accepted Answer

They cut DNA at specific sequences

Question 10

In CRISPR-Cas9 genome editing, what is the role of the PAM sequence?

Accepted Answer

It is required for Cas9 to recognize and cleave the target DNA

Question 11

RNA interference (RNAi) can be used to block gene expression by which mechanism?

Accepted Answer

Degrading target mRNA molecules

Question 12

Which of the following is essential for PCR amplification of a DNA fragment?

Accepted Answer

Primers complementary to the target sequence

Question 13

In Sanger sequencing, which component is responsible for terminating DNA strand elongation?

Accepted Answer

ddNTPs

Question 14

A child inherits a mitochondrial disease. Which parent most likely transmitted the disease, and why?

Accepted Answer

Mother, because mitochondria are inherited maternally

Question 15

A cross between two heterozygous black mice (B_ for black, b for brown) produces a 9:3:4 ratio of black:brown:white offspring. What genetic phenomenon does this illustrate?

Accepted Answer

Epistasis

Question 16

Which of the following best describes the difference between Sanger sequencing and Illumina sequencing?

Accepted Answer

Sanger sequencing uses chain-terminating nucleotides, while Illumina sequencing uses reversible terminators and massive parallelization

Question 17

A scientist uses CRISPR-Cas9 to introduce a double-strand break in a gene. If no homologous template is provided, which DNA repair pathway is most likely to occur?

Accepted Answer

Non-homologous end joining (NHEJ)

Question 18

A plant biologist clones a plant by taking a cutting and growing it into a new plant. What is true about the genotype of the new plant compared to the original?

Accepted Answer

The new plant is genetically identical to the original

Question 19

A metabolic pathway consists of three steps: $$A \rightarrow B \rightarrow C \rightarrow D. $$Mutant 1 grows only when supplied with $$C or$$ $$D$$, Mutant 2 grows only with $$D$$, and Mutant 3 grows with $$B$$, $$C$$, or $$D. $$Which enzyme is defective in Mutant 3?

Accepted Answer

The enzyme converting $$A to$$ $$B$$

Question 20

A man with an X-linked recessive disorder and a woman who is a carrier have a child. What is the probability that their son will have the disorder?

Accepted Answer

$$0.5$$

Genetics, Molecular Biology, and Inheritance: Step-by-Step Study Guidance

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