Question 1

During which specific stage of meiosis does crossing over occur, and why is this process significant for sexually reproducing organisms?

Accepted Answer

Crossing over occurs during Prophase I and is significant because it increases genetic variation among offspring.

Question 2

A woman who is heterozygous for color blindness (an X-linked recessive trait) has children with a man who is not color blind. What is the probability that their son will be color blind?

Accepted Answer

$$\frac{1}{2}$$

Question 3

Which enzyme is responsible for synthesizing short RNA primers during DNA replication, and why are these primers necessary?

Accepted Answer

Primase; the primers provide a starting point for DNA polymerase to begin synthesis.

Question 4

A plant with genotype PpYy (heterozygous for both flower color and seed shape) is crossed with another plant of the same genotype. According to Mendel's law of independent assortment, what is the expected phenotypic ratio among the offspring?

Accepted Answer

9:3:3:1

Question 5

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand.

Question 6

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; it creates a premature stop codon, likely resulting in a truncated protein.

Question 7

Which of the following scenarios best illustrates incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered plants produces all pink-flowered offspring.

Question 8

Which experiment provided the first direct evidence that DNA, not protein, is the genetic material by using radioactive labeling of viruses?

Accepted Answer

Hershey-Chase experiment

Question 9

If a DNA sample contains 30% adenine, according to Chargaff's rules, what percentage of guanine does it contain?

Accepted Answer

$$20\%$$

Question 10

Which process is responsible for removing introns from pre-mRNA in eukaryotic cells?

Accepted Answer

Splicing

Question 11

A male fruit fly with white eyes (an X-linked recessive trait) is crossed with a female who is heterozygous for red eyes. What proportion of their female offspring will have white eyes?

Accepted Answer

$$\frac{1}{2}$$

Question 12

Which of the following best describes the function of telomeres in eukaryotic chromosomes?

Accepted Answer

They protect chromosome ends from deterioration during replication.

Question 13

Which of the following mutations is most likely to result in a nonfunctional protein due to a shift in the reading frame?

Accepted Answer

Frameshift mutation

Question 14

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

Ligase

Question 15

A woman with genotype XBXb (where B = normal vision, b = color blindness) and a man with genotype XbY have a child. What is the probability that their daughter will be color blind?

Accepted Answer

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

Question 16

Which of the following best explains why males are more likely than females to express X-linked recessive traits?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will cause the trait.

Question 17

Which of the following is a real-life example of codominance in humans?

Accepted Answer

AB blood type, where both A and B antigens are expressed equally.

Question 18

Which process ensures that alleles for different traits are distributed to gametes independently of one another?

Accepted Answer

Law of Independent Assortment

Question 19

Which of the following best describes the role of the promoter region in transcription?

Accepted Answer

It is the DNA sequence where RNA polymerase binds to initiate transcription.

Question 20

A mutation in a gene results in the same amino acid being incorporated into the protein as before. What type of mutation is this, and why does it occur?

Accepted Answer

Silent mutation; it occurs because the genetic code is redundant.

Meiosis, Mendelian Genetics, Chromosomal Inheritance, DNA Structure & Replication, Gene Expression, and Mutations

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