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 zoology plant reproduction different modes of reproduction sexual and asexual reproduction lifespan, reproduction and variation

The number of chromosomes in parents and offsprings of a particular species remains constant due to

  1. Doubling of chromosomes after zygote formation

  2. Halving of chromosomes during gamete formation

  3. Doubling of chromosomes after gamete formation

  4. Halving of chromosomes after gamete formation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During gamete formation, there is meiosis in which mother cell divides into 4 cells having a half number of chromosomes. In fertilization, male and female gametes fuse to form a zygote having the same number of chromosomes as parents. Hence, the number of chromosomes remains constant.

Multiple choice biology life processes: reproduction, growth and development different types of reproduction reproductive health of humans need of family planning

If amount of DNA in sperm cell is 10 picogram, then what will be amount in microsporocyte in an phase of the cell cycle?

  1. 10 pg

  2. 20 pg

  3. 80 pg

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

  • Microsporocytes, which are diploid cells capable of undergoing meiosis to form a tetrad (four joined cells) of haploid microspores. The microspores become pollen grains and may eventually separate.
  • As we know the sperm(or male gametes) are haploid. The amount of DNA in this gametes is 10 picogram. Therefore, the amount of DNA in microsporocyte will be double i.e, 20 picograms.

So, the correct answer is " 20 pg ". 

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

What is the number of chromosomes in aleurone layer if 10 number of chromosomes are found in megaspore mother cell?

  1. 10

  2. 20

  3. 15

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If chromosomes of megaspore mother cell are 10; it ensures that the diploid number is 10. 2n = 10. Therefore, n = 5. Aleurone layer will be triploid in nature. Thus, the number of chromosomes in aleurone layer = 15.

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

The root cell of wheat plant has 42 chromosomes. What would be the number of chromosomes in the synergid cells?

  1. 7

  2. 14

  3. 21

  4. 28
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The pollen tube ultimately enters an ovule through the micropyle and penetrates one of the sterile cells on either side of the egg ( synergids). These synergids begin to degenerate immediately after pollination. 
Synergids are haploid in nature. Thus, if root cell has 2n = 42, synergids will have n = 21.

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

What would be the number of chromosomes in the cell of the aleurone layer in a plant species with 8 chromosomes in its synergids?

  1. 32

  2. 8

  3. 16

  4. 24
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Synergid is one of two small, short-lived nuclei lying near the egg in the mature embryo sac of a flowering plant. The synergids are part of the egg apparatus and are thought to help the pollen nucleus reach the egg cell for fertilization. 

The aleurone layer is the outermost layer of the endosperm, followed by the inner starchy endosperm. the cells of the aleurone layer is a triploid. 
If the synergids contain chromosomes the number of chromosomes in the aleurone layer would be since the aleurone layer is a triploid. 
 So the answer is '24'. 

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 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.