Question 1

Which eukaryotic process has no analogue in prokaryotes?

Accepted Answer

Meiosis is a unique eukaryotic process that produces haploid cells from a diploid cell through two rounds of cell division. Prokaryotes do not undergo meiosis.

Question 2

Why is meiosis sometimes called "reductive division"?

Accepted Answer

Meiosis is called "reductive division" because it results in a reduction of the number of chromosomes. In meiosis I, the homologous chromosomes pair up and exchange genetic material through crossing over, leading to the separation of the homologous pairs. Consequently, the resulting daughter cells have half the number of chromosomes (haploid) as the parent cell (diploid).

Question 3

Necrosis

Accepted Answer

Necrosis is a type of cell death that is caused by an environmental insult, such as injury or infection. It is different from apoptosis, which is a controlled and programmed type of cell death that occurs naturally. Necrosis can lead to inflammation and tissue damage in the affected area.

Question 4

You measure the overall growth of a population of cells in a cell line at a rate of 6 units per day.The rate of cell apoptosis is 4 units per day.The rate of cell division in this population is _______ units per day.

Accepted Answer

The overall growth rate of the population is the result of the balance between cell division and cell apoptosis. Since the population grows at a rate of 6 units per day and loses 4 units per day to apoptosis, the rate of cell division must be 10 units per day (6 units of growth + 4 units lost to apoptosis = 10 units of cell division).

Question 5

The normal haploid number of a plant species is 28.An individual is found with 55 chromosomes.This individual is most likely

Accepted Answer

The answer of The normal haploid number of a plant...

Question 6

If the haploid number of a mammalian cell is 32, there will be _______ sister chromatids during metaphase of mitosis.

Accepted Answer

The answer of If the haploid number of a mammalian...

Question 7

A cell in G2 has 4.8 pg of DNA.In G1, this cell had _______ pg of DNA.

Accepted Answer

During the cell cycle, DNA replication occurs during the S-phase. Therefore, the amount of DNA in the cell doubles after replication. Hence, in G1, this cell would have had half of the amount of DNA it currently has in G2, which is 2.4 pg. Therefore, the answer is C) 2.4.

Question 8

Apoptosis

Accepted Answer

Apoptosis is a highly regulated form of programmed cell death that occurs in both animals and plants. It is triggered by both internal and external signals and is highly controlled by signal transduction pathways. It occurs in various physiological processes, including development, tissue homeostasis, and immune response. Apoptosis is different from necrosis, which is a non-programmed form of cell death that occurs due to injury or damage to the cell.

Question 9

A species of grass has a haploid number of 18.How many different types of gametes can be produced from meiosis in a diploid individual just with independent assortment (no crossing over)?

Accepted Answer

The number of different types of gametes produced by a diploid individual through meiosis, considering only independent assortment and no crossing over, is calculated as 2^n, where n is the haploid number. For a species with a haploid number of 18, this results in 2^18 different types of gametes.

Question 10

An environmental change leads to cyclin being degraded at a rate much faster than normal.Such a change would tend to _______ the activity of the Cdk, which would lead to _______ phosphorylation of the target protein, which in turn would lead to _______ cells being stopped at the checkpoint.

Accepted Answer

Cyclin degradation leads to decreased activity of Cdk (cyclin-dependent kinase). Lower Cdk activity results in decreased phosphorylation of target proteins, which in turn leads to more cells being stopped at the checkpoint, as they cannot progress through the cell cycle without proper phosphorylation signals.

Question 11

In most sexually reproducing organisms, the diploid phase of the life cycle begins at

Accepted Answer

The diploid phase of the life cycle begins at fertilization, where the haploid gametes fuse and form a diploid zygote. The zygote then undergoes mitosis to form a multicellular diploid organism. Option A refers to organisms that undergo alternation of generations, where the diploid phase does begin at spore formation. Option B refers to the formation of haploid gametes, which are not yet diploid. Option C refers to meiosis, which leads to the formation of haploid cells. Option D refers to mitosis, which occurs after the diploid phase has already begun.

Question 12

Both 5-fluorouracil and paclitaxel inhibit _______, the former by _______ and the latter by blocking _______.

Accepted Answer

Both 5-fluorouracil and paclitaxel are chemotherapeutic drugs that inhibit the cell cycle. 5-fluorouracil inhibits the synthesis of thymine, which is essential for DNA replication, whereas paclitaxel blocks spindle formation during cell division. Option B correctly describes the function of both drugs.

Question 13

Which of the following is true about anaphase of mitosis?

Accepted Answer

Anaphase is the phase of mitosis when the sister chromatids of each chromosome separate and move to opposite poles of the cell. This is facilitated by the pulling force generated by the spindle fibers attached to the kinetochores of the centromeres. The other options are not correct as chromosomes line up at the equatorial plate during metaphase, the nuclear envelope breaks down during prophase, and cytokinesis occurs after telophase.

Question 14

A mutation frequently causes a chromosome of a cell line to become detached from the spindle.The most likely consequence of this mutation is that _______ cells will be stopped at the _______ checkpoint.

Accepted Answer

The spindle assembly checkpoint occurs during metaphase of mitosis (M phase) to ensure that all chromosomes are properly attached to the spindle before anaphase proceeds. A mutation causing chromosomes to detach from the spindle would likely cause more cells to be stopped at this checkpoint to prevent progression until the issue is resolved.

Question 15

In meiosis II,

Accepted Answer

In meiosis II, sister chromatids are separated, resulting in the formation of four haploid cells. However, these cells are not genetically identical due to the random distribution of homologous chromosomes during meiosis I and the possibility of crossing over. DNA replication does not occur in meiosis II as the cells produced in meiosis I already contain replicated chromosomes.

Question 16

The spindle forms during _______ of mitosis.

Accepted Answer

The spindle begins to form during prophase of mitosis, when microtubules begin to radiate out from the centrosomes at opposite ends of the cell. During metaphase, the spindle is fully formed and the chromosomes align along the middle of the spindle. In anaphase, the spindle fibers shorten, pulling the sister chromatids apart to opposite sides of the cell. In telophase, the spindle disassembles and the nuclear envelope reforms.

Question 17

Imagine that there is a mutation in the Cdk gene such that its gene product is nonfunctional.What effect would this mutation have on a mammalian white blood cell?

Accepted Answer

Cdk (Cyclin-dependent kinase) is crucial for the progression of cells through the cell cycle. It helps in DNA replication, mitosis, and overall cell reproduction by phosphorylating target proteins necessary for these processes. A nonfunctional Cdk would impair all these functions.

Question 18

Which event in prokaryotes is most like the segregation of sister chromatids in eukaryotic mitosis?

Accepted Answer

In prokaryotes, the segregation of sister chromatids is most similar to the movement of Ori regions toward opposite ends of the cell during cell division. Just like in eukaryotic mitosis, this ensures that each daughter cell receives a complete and identical copy of the genetic material.

Question 19

A cell in G2 contains 36 sister chromatids.This same cell in G1 would have

Accepted Answer

The number of chromosomes in a cell does not change during the S phase of the cell cycle (when DNA replication occurs). Thus, if a cell in G2 has 36 sister chromatids, it means it has undergone DNA replication and each chromosome has duplicated. Therefore, in G1 phase, the cell would have half the number of sister chromatids, that is, 18 chromosomes.

Question 20

In a cell in mitotic metaphase, there are 40 sister chromatids.How many centromeres are there in the cell?

Accepted Answer

In mitotic metaphase, each chromosome consists of two sister chromatids joined at a common centromere. Therefore, if there are 40 sister chromatids, they would be grouped into 20 chromosomes, meaning there are 20 centromeres.

Quiz 11: The Cell Cycle and Cell Division