Question 1

Which of the following best describes the role of ddNTPs in Sanger sequencing?

Accepted Answer

They terminate DNA strand elongation by lacking a 3' hydroxyl group.

Question 2

During PCR, which step involves the binding of primers to the single-stranded DNA template, and at what approximate temperature does this occur?

Accepted Answer

Annealing; $$50-65^\circC$$

Question 3

A researcher is analyzing a human gene using gel electrophoresis. Which property of DNA allows it to be separated by this method?

Accepted Answer

DNA's negative charge due to its phosphate backbone

Question 4

Which of the following statements about heterochromatin and euchromatin is correct?

Accepted Answer

Heterochromatin is more condensed and less transcriptionally active than euchromatin.

Question 5

Approximately what percentage of the human genome codes for functional proteins (exons)?

Accepted Answer

About 1-2%

Question 6

The C-value paradox refers to which of the following observations?

Accepted Answer

Genome size does not correlate with organismal complexity.

Question 7

If a human somatic cell is in metaphase of mitosis, how many chromosomes and chromatids are present?

Accepted Answer

$$46$$ chromosomes and $$92$$ chromatids

Question 8

Chimpanzees have 48 chromosomes, while humans have 46. What is the most widely accepted explanation for this difference?

Accepted Answer

A fusion event occurred in the human lineage, joining two ancestral chromosomes.

Question 9

Which of the following best describes the difference between meiosis I and meiosis II?

Accepted Answer

Meiosis I reduces chromosome number by half, while meiosis II separates sister chromatids.

Question 10

During which stage of meiosis does crossing over between homologous chromosomes occur, and what is the resulting structure called?

Accepted Answer

Prophase I; bivalent (tetrad)

Question 11

At the end of meiosis, what type of cells are produced and how do they differ from the original cell?

Accepted Answer

Four haploid cells, each genetically unique

Question 12

In mammals, which chromosomes determine biological sex, and what is the typical chromosomal composition for a male?

Accepted Answer

Sex chromosomes; XY

Question 13

A woman is heterozygous for a recessive X-linked disorder. What is the probability that her son will inherit the disorder, assuming the father is unaffected?

Accepted Answer

$$0.50$$

Question 14

What is X-inactivation, and what is the expected number of Barr bodies in a typical human female (XX)?

Accepted Answer

Inactivation of one X chromosome; one Barr body

Question 15

A geneticist is studying a patient with Klinefelter syndrome (XXY). How many Barr bodies would you expect to find in this individual's cells?

Accepted Answer

One

Question 16

The SRY gene is crucial for male development in mammals. What is its primary function?

Accepted Answer

It initiates the development of testes from undifferentiated gonadal tissue.

Question 17

A forensic scientist is using PCR to amplify a DNA sample from a crime scene. Which of the following equations best represents the theoretical number of DNA copies after $$n$$ cycles, starting from a single molecule?

Accepted Answer

$$2^n$$

Question 18

Which of the following best explains why most of the human genome does not code for proteins?

Accepted Answer

Most of the genome consists of regulatory sequences, introns, and repetitive DNA.

Question 19

A cell is observed to have chromosomes aligned at the metaphase plate, each consisting of two sister chromatids. Which stage of the cell cycle is this cell in?

Accepted Answer

Metaphase of mitosis

Question 20

Which of the following scenarios best illustrates sex-linked inheritance?

Accepted Answer

A trait that is more common in males and is inherited from mothers to sons.

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