Question 1

During which phase of the cell cycle does DNA replication occur, and what is the consequence for the amount of DNA in a human cell at the end of this phase?

Accepted Answer

S phase; the DNA content is doubled compared to the original cell.

Question 2

Which enzyme is responsible for relieving the tension ahead of the replication fork during DNA replication, and what would happen if this enzyme were nonfunctional?

Accepted Answer

Topoisomerase; DNA supercoiling would hinder replication.

Question 3

A human cell in G1 phase contains 10 picograms of DNA. After S phase, how much DNA would you expect to find, and after which phase would it return to 10 picograms?

Accepted Answer

20 picograms after S phase; returns to 10 picograms after mitosis.

Question 4

Why is DNA replication described as 'semi-conservative'?

Accepted Answer

Each new DNA molecule contains one old and one new strand.

Question 5

Which of the following best describes the difference between metaphase of mitosis and metaphase I of meiosis in a diploid cell with four chromosomes?

Accepted Answer

In mitosis, sister chromatids align at the metaphase plate; in meiosis I, homologous chromosomes (tetrads) align together.

Question 6

What is the main function of telomerase in human cells, and which cells typically have the highest telomerase activity?

Accepted Answer

To add repetitive sequences to chromosome ends; highest in germ cells.

Question 7

Which of the following events increases genetic diversity in gametes produced by meiosis?

Accepted Answer

Crossing over during prophase I and independent assortment during metaphase I.

Question 8

Which checkpoint in the cell cycle is most important for preventing uncontrolled cell division, and which protein is heavily involved at this checkpoint?

Accepted Answer

G1 checkpoint; p53 protein.

Question 9

A mutation converts a proto-oncogene into an oncogene. What is the likely consequence for the cell?

Accepted Answer

The cell will divide uncontrollably, increasing cancer risk.

Question 10

Which of the following best describes the difference between simple diffusion and facilitated diffusion across a cell membrane?

Accepted Answer

Facilitated diffusion requires membrane proteins, while simple diffusion does not.

Question 11

Which type of bond is most abundant in hydrophobic molecules?

Accepted Answer

Nonpolar covalent bonds

Question 12

What is the primary function of the rough endoplasmic reticulum (Rough ER) in eukaryotic cells?

Accepted Answer

Protein synthesis and modification

Question 13

Which process describes the movement of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration?

Accepted Answer

Osmosis

Question 14

Which part of an amino acid determines whether a protein is hydrophobic or hydrophilic?

Accepted Answer

The R group (side chain)

Question 15

Which of the following best explains why proteins can perform a wider variety of functions than other macromolecules?

Accepted Answer

Proteins have diverse structures due to 20 different amino acids.

Question 16

Which of the following is a correct description of the bonds that join nucleotides in DNA and RNA?

Accepted Answer

Phosphodiester bonds

Question 17

Which process occurs in both prokaryotes and eukaryotes, and where does it take place in each?

Accepted Answer

Transcription; nucleus in eukaryotes, cytoplasm in prokaryotes

Question 18

Which of the following best describes the difference between competitive inhibition and allosteric inhibition of an enzyme?

Accepted Answer

Competitive inhibitors bind to the active site; allosteric inhibitors bind to a different site.

Question 19

Which process in cellular respiration produces the most ATP, and where does it occur?

Accepted Answer

Electron transport chain and oxidative phosphorylation; inner mitochondrial membrane

Question 20

According to the theory of endosymbiosis, which organelles are believed to have originated from free-living prokaryotes?

Accepted Answer

Mitochondria and chloroplasts

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