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 botany asexual and sexual reproduction in plants structure of male and female reproductive structures structure of ovule gynoecium

If spores have 10 chromosomes and 20 picogram DNA then what would be the chromosome number and DNA amount in spore mother cell at the end of S-phase in the life cycle of the same plant?

  1. 40 chromosomes and 80 pg DNA

  2. 20 chromosomes and 80 pg DNA

  3. 20 chromosomes and 40 pg DNA

  4. 40 chromosomes and 40 pg DNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Spores are haploid (n=10, DNA=20pg). The spore mother cell (SMC) is diploid (2n=20, DNA=40pg). During the S-phase, DNA replicates, doubling the DNA content to 80pg, while the chromosome number remains 20.

Multiple choice bio-chemistry biological oxidation chemiosmotic hypothesis living organisms and energy production mechanism of photosynthesis

Which of the following is an incorrect combination of organism with its chromosome number in mieocyte and in gamete?

  1. Onion, $24, 12$
  2. Ophioglossum, $1260, 630$
  3. Human beings, $46, 23$
  4. Fruit fly, $8, 4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Chromosome number in meiocyte $(2n)$ of onion cell is $32$, while chromosome number in gamete $(n)$ is $16$.

Multiple choice botany plant breeding method of plant breeding for crop improvement plant breeding for food production biotechnology

How many meiotic divisions are necessary for the formation of 100 grains of wheat?

  1. 100

  2. 125

  3. 25

  4. 50
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
For formation of 100 grains, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic division).
Hence, number of meiotic divisions necessary for 100 grains formation$ = 25 + 100 = 125$.
Multiple choice biology structure of chromosome, cell cycle and cell division cell division in embryo development mitosis division for growth and reproduction

In animal cells, cytokinesis involves 

  1. Separation of sister chromatids

  2. Contraction of ring of microfilaments

  3. Depolymerisation of kinetochore microtubules

  4. Protein kinase that phosphorylates other enzymes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During cytokinesis in animal cells, a contractile ring composed of actin microfilaments and myosin forms beneath the plasma membrane. The constriction of this ring pinches the cell into two daughter cells.

Multiple choice biology structure of chromosome, cell cycle and cell division cell division in embryo development mitosis division for growth and reproduction

In animal cytokinesis, cleavage occurs with the help of

  1. Microtubules

  2. Spindle fibres

  3. Microfibrils

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

In animal cells, cytokinesis is achieved by the formation of a contractile ring composed of actin microfilaments, which pinches the cell membrane inward.

Multiple choice biology structure of chromosome, cell cycle and cell division cell division in embryo development mitosis division for growth and reproduction

Cytochalasin B is a drug isolated from moulds. It blocks the formation of contractile microfilaments. Which of the following aspects of the cell cycle would be most disrupted due to this ?

  1. Cleavage furrow formation

  2. Attachment of kinetochore to spindle fibres

  3. Spindle fibre formation

  4. Cell elongation during anaphase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Spindle formation is mainly done by centrioles. It helps in separation of chromosomes during cell division. Cytochalasin B is a cell-permeable mycotoxin. It inhibits cytoplasmic division by blocking the formation of contractile microfilaments due to which cell is unable to maintain the desired number of chromosomes and leads to numerical abberations.

Multiple choice evs farming brings prosperity agriculture and types of crops crop management management of crops in india

In the hexaploid wheat, the haploid(n) and basic (x) numbers of chromosomes are?

  1. $n=21$ and $x=21$
  2. $n=21$ and $x=14$
  3. $n=21$ and $x=7$
  4. $n=7$ and $x=21$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Haploid means half the number of total chromosomes formed during gamete formation. n=21.
  • total no. of chromosomes in hexaploid wheat=42.
  • the basic set no. of chromosomes (x)= 42/6=7
  • So, the correct option is 'n=21n=21 and 
    x=7'.
Multiple choice biology for the continuity of generation fertilization in human being fertilization in humans human fertilization

A human zygote has 

  1. 46 chromosomes

  2. 23 chromosomes

  3. 47 chromosomes

  4. 48 chromosomes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Zygote or the fertilized egg cell results from the union of a female gamete (Egg or ovum) with a male gamete (sperm). The number of chromosomes in the gamete is haploid and human gametes contain 23 chromosomes. As zygote is from the fusion of two gametes, the chromosome number is diploid and is double of that in gamete and thus has 46 chromosomes.

Multiple choice biology for the continuity of generation fertilization in human being fertilization in humans human fertilization

Is the chromosome number of the zygote, embryonal cells, and adult of a particular organism always constant? How is the constancy maintained in these three stages?

  1. Yes, by mitosis

  2. Yes, by meiosis

  3. No, by meiosis

  4. No, by mitosis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • A zygote is the fertilized egg that results from the union of male and female gametes. Once, the zygote is formed, 
  • it undergoes mitotic divisions. Embryonal cells also divide by mitosis to produce more of its kind. The cells in the adult organism also divide by mitosis.
Mitosis is a type of cell division in which the chromosomes in a cell nucleus are separated into two equal sets of chromosomes, each in its own nucleus.

Thus, the correct answer is option A.

Multiple choice biology for the continuity of generation fertilization in human being fertilization in humans human fertilization

What would be the ratio of chromosome number between an egg and its zygote? 

  1. 1 : 2

  2. 2 : 2

  3. 1 : 3

  4. 2 : 1
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The egg is the female gamete and is haploid in nature containing 'n' number of chromosomes. Zygote is formed by the fusion of male and female gametes and is thus diploid in nature and contains '2n' number of chromosomes.
Thus, the correct answer is option A.

Multiple choice expression of gene inherited changes biology

Telomere of eucaryotic chromosome possesses short segments of

  1. Guanine rich repeats

  2. Thymine rich repeats

  3. Cytosine rich repeats

  4. Adenine rich repeats
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Telomeres, the ends of eukaryotic chromosomes, consist of repetitive DNA sequences that are typically rich in guanine.

Multiple choice zoology immunity phagocytosis cells in immune system immune system, its cells, mediators and antigens

MHC genes in humans are located on 

  1. Chromosome 1.

  2. Chromosome 2.

  3. Chromosome 4.

  4. Chromosome 6.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Major histocompatibility complex (MHC) are the proteins on the surface of cell membrane. These proteins play an important role in the recognition of the foreign antigens. There are two MHC complexes called as MHC-I and MHC-II complex. These complexes play a different role in different processes. The genes for MHC complex are located on the chromosome 6 in the case of humans. In the case of mice, these genes are on chromosome 17. 

Thus, the correct answer is option D. 

Multiple choice botany asexual and sexual reproduction in plants introduction to flower pre fertilization - plants modes of reproduction

Meiotic division occurring just at the time of gametogenesis is 

  1. Sporic

  2. Initial

  3. Intermediate

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

  • In plants, meiosis is occurring as in diploid sporophyte to produce haploid spores. 
  • The haploid spores are germinating to produce structures called gametophytes. The gametophytes then produce gametes. 
  • Gametic or the terminal meiosis occurs in all multicellular animals. It takes place in the gonads and hence as results in the formation of gametes. 
  • It is responsible for gametogenesis and does not give rise to gametophytes.
  • The correct option is D.