Biology

Cell Cycle and Chromosomes

1,219 Questions

Explore a curated list of questions covering the cell cycle, mitosis, and meiosis. Topics include DNA replication, chromosomal structures, and genetic disorders. This material is essential for students preparing for biology and general science competitive exams.

Cell cycle eventsDNA replicationMeiosis processChromosomal structuresGenetic disorders

Cell Cycle and Chromosomes Questions

Multiple choice

Select the correct statement regarding mitosis in humans.

  1. All body cells undergo the process of mitosis continously from the date of conceiving till death.

  2. Every body cell going through the process of mitosis divides into two complete new cells that are usually identical to the cell from which they formed.

  3. It takes about three days for a cell to complete all six phases of mitosis.

  4. Through mitosis, body produces new sex cells.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Both the original and the new cells normally are identical in their components and functions. This assures that replacement cells in skin and other body tissues are faithful copies.

Multiple choice

A cell cultured in colchicines undergoes a complete cell cycle, except for the fact that chromosomes donot migrate to the poles during anaphase. What can be concluded from this?

  1. Colchicines do not affect the microtubules.

  2. DNA replication does not necessarily results in the chromosome separation.

  3. Centromere represent under replicated DNA.

  4. Spindle is made after interphase.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Colchicine inhibits microtubule polymerization, preventing spindle fiber formation during mitosis. Since chromosomes cannot attach to spindle fibers, they fail to separate and migrate to opposite poles during anaphase. DNA replication occurs normally in S phase, but chromosome segregation cannot complete without functional microtubules.

Multiple choice

When the nucleus of a red blood cell present in a frog, which does not replicates DNA, is transplanted into an enucleated frog egg, the egg goes through several cell divisions. Which of the following is the best interpretation for this phenomenon?

  1. Isolated red blood cell nuclei synthesises DNA.

  2. Nucleus plays no role in cell division.

  3. Enucleated frog egg can divide.

  4. Cytoplasm controls nuclear DNA replication.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a differentiated nucleus (from red blood cell that doesn't normally replicate DNA) is transplanted into an enucleated egg, the egg's cytoplasm reprograms the nucleus. The cytoplasm contains factors that can reactivate dormant genes and initiate DNA replication and cell division, demonstrating that cytoplasmic factors control nuclear activity.

Multiple choice

Match the following:

 
Column A Column B
1. DNA found at the ends of linear eukaryotic chromosomes A. centromere
2. Protein structure on eukaryotic chromosomes where spindle fibers attach B. telomere
3. DNA site where kinetochores are found C. nucleolar organizer
4. DNA sequence that serves as the template for the synthesis and amplification of ribosomal DNA D. inetochore

  1. 1 – A, 2 – D, 3 – B, 4 – C

  2. 1 – B, 2 – D, 3 – A, 4 – C

  3. 1 – D, 2 – C, 3 – A, 4 – B

  4. 1 – C, 2 – D, 3 – C, 4 – B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Telomeres are DNA sequences at chromosome ends (1-B). Kinetochores are protein structures where spindle fibers attach (2-D). Centromeres are DNA sites where kinetochores are found (3-A). Nucleolar organizers are DNA sequences that serve as templates for ribosomal RNA synthesis and amplification (4-C). Option B correctly matches these.

Multiple choice

A cell has ‘c’ as the DNA content and ‘n’ as the number of chromosomes. What would be the value of ‘c’ and ‘n' immediately before the cell division in case of mitosis?

  1. 2c and 4n respectively

  2. 4c and 4n respectively

  3. 4c and 2n respectively

  4. 2c and 2n respectively
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At the beginning of the cell cycle, a diploid cell has 2c DNA content and 2n chromosomes. After S phase (DNA replication), before mitosis begins, the cell has doubled DNA content (4c) but still has the same number of chromosomes (4n sister chromatids). Immediately before mitosis, after replication is complete, the cell contains 4c DNA and 4n chromatids.

Multiple choice

When an animal virus becomes integrated into the host’s chromosome, it is then called

  1. prophage

  2. temperate virus

  3. provirus

  4. coliphage
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When an animal virus integrates its genetic material into the host chromosome, it becomes a provirus. This is distinct from a prophage (term used for bacteriophages integrated into bacterial DNA). The integrated viral genome can remain dormant or be activated to produce new virus particles. Temperate virus refers to the virus type, not the integrated state, and coliphage refers to bacteriophages infecting E. coli.

Multiple choice

Why would you predict that half of the human babies born will be males and half will be females?

  1. Because of the segregation of the X and Y chromosomes during male meiosis

  2. Because of the segregation of the X chromosomes during female meiosis

  3. Because all eggs contain an X chromosome

  4. Because, on average, one-half of all eggs produce females
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The equal sex ratio at birth occurs because during male meiosis, X and Y chromosomes segregate randomly into different sperm cells. Each sperm carries either X or Y, and fertilization of an X-bearing egg is equally likely with either type. Egg cells always contain X chromosomes, so they don't determine sex - the sperm does.

Multiple choice

Philadelphia chromosome is generated by translocation between

  1. chromosome 18 and chromosome 6

  2. chromosome 22 and chromosome 9

  3. chromosome 22 and chromosome 3

  4. chromosome 16 and chromosome 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Philadelphia chromosome is formed by a reciprocal translocation between chromosome 9 and chromosome 22, specifically t(9;22)(q34;q11). This creates the BCR-ABL fusion gene associated with chronic myeloid leukemia. The other chromosome pairs listed are involved in different translocations.

Multiple choice

The bridge-fragment configuration at anaphase-1 is characteristic of

  1. translocation heterozygote

  2. paracentric inversion heterozygote

  3. pericentric inversion heterozygote

  4. duplication heterozygote
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During anaphase I in paracentric inversion heterozygotes, a bridge-fragment configuration forms because crossing over within the inversion creates a dicentric chromosome (forms a bridge) and an acentric fragment (lacks a centromere). Translocation heterozygotes form quadrivalents, pericentric inversions don't produce this pattern, and duplications don't create bridges.

Multiple choice

Down’s syndrome is characterised by

  1. 21 trisomy

  2. two X and one Y chromosomes

  3. 19 trisomy

  4. only one X chromosome
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

People affected with Down’s syndrome have 21 trisomy (an extra chromosome number 21). So, their chromosome count is 47 (45 + XX in females and 45 + XY in males).

Multiple choice

In oogenesis after arrival of spermatozoa, completion of meiosis takes place by ____________.

  1. restarting the cell cycle by breaking down MPF and turning on APC

  2. restarting the cell cycle by breaking down APC and turning on MPF

  3. formation of first polar body

  4. formation of second polar body

  5. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Secondary oocyte starts meiosis II and proceeds upto metaphase II, further development starts only after the arrival of spermatozoa. Entery of sperm restarts the cell cycle by breaking down MPF(M-phase promoting factor) and turning on APC(Anaphase promoting complex).