Question 1

Which experiment provided the strongest evidence that DNA, rather than protein, is the genetic material in cells?

Accepted Answer

The Hershey-Chase experiment using bacteriophages labeled with $$^{32}P$$ and $$^{35}S$$

Question 2

A researcher isolates a DNA molecule and finds that it denatures at a higher temperature than another DNA sample of the same length. What is the most likely explanation for this observation?

Accepted Answer

The DNA sample has a higher proportion of guanine-cytosine (G-C) base pairs

Question 3

Which of the following best describes the function of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes to prevent shortening during replication

Question 4

A mutation in the gene encoding the lac repressor (lacI) results in a nonfunctional protein. What is the most likely effect on the expression of the lac operon in E. coli?

Accepted Answer

The lac operon will be constitutively expressed, even in the absence of lactose

Question 5

Which of the following statements about eukaryotic mRNA processing is correct?

Accepted Answer

Introns are removed and exons are joined together by the spliceosome

Question 6

A patient is diagnosed with a genetic disease caused by a trinucleotide repeat expansion. Which of the following best explains the molecular basis of this mutation?

Accepted Answer

A segment of DNA with three nucleotides is abnormally repeated multiple times

Question 7

During DNA replication in E. coli, which enzyme is responsible for synthesizing the RNA primer required for DNA polymerase to begin synthesis?

Accepted Answer

Primase

Question 8

Which of the following best describes the role of the Origin Recognition Complex (ORC) in eukaryotic DNA replication?

Accepted Answer

It binds to origins of replication and helps recruit other proteins necessary for initiation

Question 9

A scientist is using the Sanger (dideoxy) method to sequence DNA. Which of the following is essential for chain termination during this process?

Accepted Answer

Incorporation of dideoxynucleotides (ddNTPs)

Question 10

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Multiple codons can specify the same amino acid

Question 11

A cell is exposed to ultraviolet (UV) radiation, resulting in the formation of thymine dimers. Which DNA repair mechanism is most directly involved in correcting this type of damage?

Accepted Answer

Nucleotide excision repair

Question 12

Which of the following statements about the cell cycle is correct?

Accepted Answer

The mitotic index is the proportion of cells in mitosis at a given time

Question 13

A researcher is studying a eukaryotic gene that is only expressed when its chromatin is in a decondensed state. Which of the following modifications is most likely associated with this gene's active state?

Accepted Answer

Histone acetylation

Question 14

Which of the following best describes the function of the anaphase-promoting complex (APC) during mitosis?

Accepted Answer

It triggers the degradation of securin, allowing separase to cleave cohesin and initiate chromatid separation

Question 15

A patient with chronic myeloid leukemia (CML) is found to have the Philadelphia chromosome. What is the molecular basis of this abnormality?

Accepted Answer

A chromosomal translocation resulting in a BCR-ABL fusion gene

Question 16

Which of the following is a key difference between prokaryotic and eukaryotic transcription?

Accepted Answer

Eukaryotic mRNAs are typically processed with a 5' cap and 3' poly(A) tail

Question 17

A scientist is using a yeast two-hybrid (Y2H) system to study protein-protein interactions. Which of the following best describes the principle behind this technique?

Accepted Answer

It uses two fusion proteins, one with a DNA-binding domain and one with an activation domain, to reconstitute transcription if the proteins interact

Question 18

Which of the following best explains the role of microRNAs (miRNAs) in gene regulation?

Accepted Answer

They bind to complementary mRNA sequences and inhibit translation or promote degradation

Question 19

A cell is exposed to a chemical that inhibits the function of the retinoblastoma (Rb) protein. What is the most likely consequence for the cell cycle?

Accepted Answer

The E2F transcription factor will be constitutively active, promoting uncontrolled entry into S phase

Cell Biology: Molecular Genetics, Gene Expression, Cell Cycle, and Cancer – Comprehensive Study Notes

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