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

During zygotene stage of meiosis in a spore mother cell, a proteinaceous structure which appears between homologous chromosomes is known as

  1. histone complex

  2. lysosomal complex

  3. liposomal complex

  4. synaptonemal complex
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The synaptonemal complex is a protein structure that forms between homologous chromosomes during the zygotene stage of prophase I in meiosis. It facilitates synapsis (pairing) of homologous chromosomes and crossing over. This matches option D. The other options refer to different cellular structures: histone complexes (DNA packaging), lysosomal complexes (digestion), and liposomal complexes (lipid transport).

Multiple choice

With reference to sex determination in Melandrium album, consider the following statement:

  1. The Y chromosome is longer than the X chromosome.

  2. The Y chromosome and X chromosome form a heteromorphic bivalent at meiosis.

  3. It is the presence of a single Y chromosome rather than any number of X chromosomes or autosomes that give a male individual.

Which of the statements given above are correct?

  1. 1 and 2 only

  2. 2 and 3 only

  3. 1 and 3 only

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

In Melandrium album (now classified as Silene latifolia), the Y chromosome is longer than X, they form heteromorphic bivalents, and the presence of a Y chromosome determines maleness regardless of the number of X chromosomes. Statement 2 is incorrect because Y and X are heteromorphic (different in size and structure), not homomorphic.

Multiple choice

Double trisomes have a genomic constitution of

  1. 2n + 2

  2. 2n + 1 + 1

  3. 2n + 1

  4. 2n - 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A double trisome involves two different chromosomes, each present in three copies instead of the normal two copies. This is represented as 2n + 1 + 1, indicating an extra copy of two different chromosomes. A simple trisome would be 2n + 1.

Multiple choice

Assertion (A) : Segmental allopolyploids where all the chromosomes are homologous.

Reason (R) : Segmental allopolyploids can be identified by their meiotic behaviour.

  1. Both A and R are individually true and R is the correct explanation of A.

  2. Both A and R are individually true but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Segmental allopolyploids have chromosomes that are partially homologous (some chromosomes pair, others don't). Both statements are true - they do have homologous chromosomes (A is true), and their meiotic behaviour (irregular pairing) is used to identify them (R is true). However, R is not the EXPLANATION of A - meiotic behaviour doesn't cause the chromosomes to be homologous; the homology exists independently and is revealed by meiosis.

Multiple choice

Dense clumping of chromosomes on one side with no chromatin material being seen in the rest of the nucleus is termed as

  1. synapsis

  2. synizesis

  3. congression

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

 Synizesis refers to a phenomenon sometimes observed in one of the subphases of meiosis. This phenomenon, sometimes referred to as a 'synizetic knot', and contrasted with the chromosome 'bouquet' more typically observed, is characterized by the localization of the meiotic chromosomes in a tight clump on one side of the nucleus.

Multiple choice

An unfertilised egg always has

  1. X chromosome

  2. Y chromosome

  3. a pair of X and Y chromosomes

  4. no chromosome
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A female egg has X chromosome.

Multiple choice

The karyotypes found in normal human sperm is

  1. 23, Y

  2. 23, X

  3. 46, XX

  4. 46, XY
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Human sperm and egg are in the haploid states, i.e. they only have one copy of each chromosome, or 22 autosomes and one sex chromosome (either X or Y). Therefore, the most likely karyotype, of those listed, to be found in normal human sperm is 23, X. 23, Y is an equally likely karyotype in normal sperm.