In most prokaryotes, the genome is a single circular DNA molecule.
Correct Answer
True
True. A typical bacterium carries one double-stranded, circular chromosome in its nucleoid, unlike the several linear chromosomes of a eukaryote.
Category: The Genome
Question 2
Human somatic cells contain 46 pairs of chromosomes.
Correct Answer
False
False. Human somatic cells contain 46 chromosomes in total, arranged as 23 pairs of homologous chromosomes.
Category: The Genome
Question 3
A gene can exist in different versions, such as the A, B and O versions of the human blood type gene.
Correct Answer
True
True. Homologous chromosomes carry the same genes, but the versions inherited from each parent can differ. A person inherits two of the A, B and O versions, one from each parent.
Category: The Genome
Question 4
The X and Y chromosomes are fully homologous along their entire length.
Correct Answer
False
False. The X and Y chromosomes share only a small region of homology, and most of their genes differ. They are the exception to the rule that chromosome pairs match.
Category: The Genome
Question 5
During G1, the cell is metabolically inactive and makes almost no new proteins.
Correct Answer
False
False. G1 is a biochemically active growth period in which the cell makes proteins, builds up DNA building blocks and stores energy for replication, even though little change is visible.
Category: Interphase and Checkpoints
Question 6
The centrosome is duplicated during interphase, before mitosis begins.
Correct Answer
True
True. The centrosome duplicates during interphase, around the time the DNA is replicated, and finishes by G2, giving the cell two centrosomes to organize the spindle.
Category: Interphase and Checkpoints
Question 7
Cells in G0 are actively preparing to divide.
Correct Answer
False
False. Cells in G0 are quiescent: they have left the cell cycle and are not preparing to divide. Some return to G1 when signaled, and others stay in G0 permanently.
Category: Interphase and Checkpoints
Question 8
The M checkpoint occurs at the start of prophase.
Correct Answer
False
False. The M checkpoint, also called the spindle checkpoint, occurs near the end of metaphase, just before sister chromatids separate.
Category: Interphase and Checkpoints
Question 9
During prophase, the nucleolus becomes larger and more visible.
Correct Answer
False
False. The nucleolus disappears during prophase as the nucleus breaks down. It reappears after mitosis when new nuclei form.
Category: Mitosis
Question 10
Kinetochores attach to spindle microtubules during prometaphase.
Correct Answer
True
True. In prometaphase the last of the nuclear envelope disappears and protein kinetochores at each centromere attach to spindle microtubules.
Category: Mitosis
Question 11
Chromosomes are at their least condensed during metaphase.
Correct Answer
False
False. Chromosomes are at their most condensed during metaphase, when they line up at the center of the cell.
Category: Mitosis
Question 12
During anaphase, the cell elongates as non-kinetochore microtubules slide past each other.
Correct Answer
True
True. While kinetochore microtubules pull the separated chromosomes to the poles, overlapping non-kinetochore microtubules slide apart and stretch the cell.
Category: Mitosis
Question 13
During telophase, a nuclear envelope re-forms around each set of chromosomes.
Correct Answer
True
True. In telophase the chromosomes reach the poles and decondense, the spindle is taken apart, and a new nuclear envelope forms around each set.
Category: Mitosis
Question 14
Plant cells and most fungi have centrioles in their centrosomes.
Correct Answer
False
False. Many eukaryotes, including plants and most fungi, lack centrioles, yet they still form a spindle and divide. Animal cell centrosomes contain a pair of centrioles.
Category: Mitosis
Question 15
In animal cells, a ring of actin filaments pinches the cell in two during cytokinesis.
Correct Answer
True
True. A contractile ring of actin filaments forms just inside the plasma membrane at the former metaphase plate and draws it inward, forming a cleavage furrow that deepens until the cell divides.
Category: Cytokinesis
Question 16
An oncogene is a mutated form of a proto-oncogene.
Correct Answer
True
True. A proto-oncogene is a normal gene for a positive regulator of the cycle. A mutation that increases its activity turns it into an oncogene, which can drive uncontrolled division.
Category: Cancer and Cell Cycle
Question 17
Binary fission produces two daughter cells that are genetically identical to the parent cell.
Correct Answer
True
True. The circular chromosome is copied and one copy goes to each daughter cell, so both are genetically identical to the parent. In a single-celled prokaryote each daughter is a new individual.
Category: Prokaryotic Division
Question 18
Bacterial DNA replication proceeds in only one direction around the circular chromosome.
Correct Answer
False
False. Bacterial replication is bidirectional: starting at the origin of replication, it moves in both directions around the circle at once.
Category: Prokaryotic Division
Question 19
The septum in a dividing bacterium grows from the center of the cell outward to its edge.
Correct Answer
False
False. The septum grows from the edge of the cell inward toward the center, guided by the FtsZ ring, until new walls separate the two daughter cells.
Category: Prokaryotic Division
Question 20
FtsZ is structurally similar to tubulin, suggesting the two proteins share a common ancestor.
Correct Answer
True
True. FtsZ and tubulin are homologous: both are GTP-binding proteins that polymerize into filaments, FtsZ into the division ring and tubulin into microtubules. Tubulin is thought to have evolved from an FtsZ-like prokaryotic protein.
Category: Prokaryotic Division