IMAT - International Medical Admissions Cellular Biology and Division Questions and Answers — Questions and Answers
Question 1: A scientist is studying a cell that has just passed the G1 checkpoint. Which of the following processes is the cell now irreversibly committed to?
- Synthesizing proteins for mitosis
- Replicating its DNA (Correct answer)
- Undergoing cytokinesis
- Entering the G0 resting phase
Correct answer: Replicating its DNA
The G1 checkpoint is a critical point in the cell cycle. Once a cell passes this checkpoint, it is committed to proceeding with cell division. The next phase after G1 is the S phase, where DNA synthesis or replication occurs. The other options are incorrect as protein synthesis for mitosis occurs later in G2, cytokinesis is the final stage of cell division, and entering G0 is a path taken by cells that do not pass the G1 checkpoint.
Question 2: Which of the following correctly describes a key difference between mitosis and meiosis?
- Mitosis results in four genetically distinct haploid cells, while meiosis produces two identical diploid cells.
- Crossing over between homologous chromosomes occurs only during prophase of mitosis.
- Mitosis is involved in growth and repair, while meiosis produces gametes for sexual reproduction. (Correct answer)
- Both processes consist of two rounds of nuclear division.
Correct answer: Mitosis is involved in growth and repair, while meiosis produces gametes for sexual reproduction.
Mitosis is a process of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information; these cells are our sex cells – sperm in males, eggs in females. Crossing over is unique to meiosis I. Mitosis has one round of division, while meiosis has two.
Question 3: A new drug is developed that inhibits the function of the Golgi apparatus. A cell treated with this drug would be unable to properly perform which of the following functions?
- Synthesizing lipids and detoxifying poisons
- Generating ATP through cellular respiration
- Replicating DNA before cell division
- Modifying, sorting, and packaging proteins and lipids (Correct answer)
Correct answer: Modifying, sorting, and packaging proteins and lipids
The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. Lipid synthesis and detoxification occur in the smooth endoplasmic reticulum. ATP generation happens in the mitochondria. DNA replication occurs in the nucleus.
Question 4: During which phase of meiosis do homologous chromosomes separate and move to opposite poles of the cell?
- Anaphase II
- Prophase I
- Anaphase I (Correct answer)
- Metaphase II
Correct answer: Anaphase I
Anaphase I is the stage of meiosis where homologous chromosomes are pulled apart and move to opposite ends of the cell. In Anaphase II, it is the sister chromatids that separate. In Prophase I, homologous chromosomes pair up and crossing over occurs. In Metaphase II, chromosomes line up at the metaphase plate.
Question 5: A patient is diagnosed with a condition where their cells are unable to break down and recycle waste products, leading to an accumulation of cellular debris. This condition is most likely caused by a malfunction in which organelle?
- Ribosomes
- Lysosomes (Correct answer)
- Mitochondria
- The nucleus
Correct answer: Lysosomes
Lysosomes are membrane-bound organelles that contain digestive enzymes. They are involved in breaking down excess or worn-out cell parts, as well as destroying invading viruses and bacteria. Ribosomes are responsible for protein synthesis, mitochondria for energy production, and the nucleus contains the cell's genetic material.
Question 6: Which of the following is assessed at the M (spindle) checkpoint during the cell cycle?
- Whether the DNA has been completely replicated without damage
- Whether the cell is large enough to divide
- Whether all sister chromatids are correctly attached to the spindle microtubules (Correct answer)
- Whether there are sufficient growth factors to stimulate division
Correct answer: Whether all sister chromatids are correctly attached to the spindle microtubules
The M checkpoint, or spindle checkpoint, occurs during metaphase and ensures that all sister chromatids are properly attached to the spindle fibers. This is crucial for the correct segregation of chromosomes into the daughter cells. DNA integrity is checked at the G1 and G2 checkpoints, cell size is checked at the G1 checkpoint, and the presence of growth factors is an external signal that influences the G1 checkpoint.
IMAT - International Medical Admissions Cellular Biology and Division Questions and Answers
A scientist is studying a cell that has just passed the G1 checkpoint.
Which of the following processes is the cell now irreversibly committed to?