Question 1

Which experiment provided the first direct evidence that DNA is the molecule responsible for heredity in bacteria?

Accepted Answer

The Griffith transformation experiment with Streptococcus pneumoniae

Question 2

What is the primary function of fibroblasts at a wound site?

Accepted Answer

To divide and secrete extracellular matrix components such as collagen and fibronectin

Question 3

Which checkpoint ensures that all chromosomes are properly attached to spindle microtubules before anaphase begins?

Accepted Answer

Mitotic (spindle assembly) checkpoint

Question 4

A mutation in a gene required for the spindle assembly checkpoint could result in which of the following outcomes?

Accepted Answer

Cells with abnormal numbers of chromosomes

Question 5

Which of the following best describes the role of platelet-derived growth factor (PDGF) in cell culture?

Accepted Answer

It acts as a signal that stimulates cell division

Question 6

In the Hershey-Chase experiment, why was $$^{32}P$$ used to label DNA?

Accepted Answer

Because phosphorus is a component of DNA but not proteins

Question 7

According to Chargaff’s rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

$$20\%$$

Question 8

Which of the following scenarios best illustrates the concept of transformation as described by Griffith?

Accepted Answer

A bacterium acquires antibiotic resistance after exposure to DNA from a resistant strain

Question 9

What would most likely happen if a cell’s G1/S checkpoint fails to function properly?

Accepted Answer

The cell may enter S phase without sufficient nutrients or signals, leading to abnormal division

Question 10

Which of the following is a direct consequence of a cell ignoring inhibitory signals that normally prevent division?

Accepted Answer

The cell will undergo uncontrolled division, potentially leading to cancer

Question 11

Which of the following best explains why proteins were initially considered better candidates than DNA for carrying genetic information?

Accepted Answer

Proteins are composed of 20 different amino acids, allowing for greater complexity

Question 12

If a cell receives a go-ahead signal at the G1 checkpoint, what is the most likely outcome?

Accepted Answer

The cell will complete S, G2, and M phases and divide, provided it passes other checkpoints

Question 13

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype refers to the genetic blueprint, while phenotype refers to observable traits

Question 14

A scientist isolates DNA from a new species and finds that $$A = 22\%$$ and $$C = 28\%. $$According to Chargaff’s rules, what is the percentage of $$T$$?

Accepted Answer

$$22\%$$

Question 15

Which of the following is a real-world example of a mutation leading to cancer?

Accepted Answer

A mutation in a gene encoding a checkpoint protein causes the cell to divide without proper chromosome attachment

Question 16

Which of the following best describes the outcome of the Hershey-Chase experiment?

Accepted Answer

Radioactive phosphorus was found inside the bacteria, proving DNA is the genetic material

Question 17

Which of the following is a function of the anaphase-promoting complex (APC) during mitosis?

Accepted Answer

It degrades securin, allowing separase to cleave cohesin and initiate anaphase

Question 18

A cell is observed to have both kinetochores of a chromosome attached to spindle microtubules from opposite poles. What is the next step in mitosis?

Accepted Answer

The cell will proceed to anaphase

Question 19

Which of the following best explains why cancer cells can divide uncontrollably?

Accepted Answer

They ignore signals that normally regulate the cell cycle, such as growth factors and inhibitory signals

Question 20

Which of the following is a direct result of the loss of contact inhibition in cells?

Accepted Answer

Cells continue to divide even when crowded, leading to tumor formation

LEC 17: Cell Cycle Regulation, Growth Factors, and the Discovery of DNA as Genetic Material

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