Biology

Cell Cycle and Chromosomes

1,348 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

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).