Cell Cycle and Cell Division Test - 70

In mitosis DNA content is doubled during S phase resulting in 2n chromosomes having two chromatids. These 2 chromatids of 2n get arranged at metaphase plate in metaphase. And in anaphase, the 2 chromatids of 2n chromosomes are separated from each other . so the cell during this phase becomes 4n.

Calcium is the element which involves in the formation of mitotic spindles. It will be found in the meristems (meristems are the regions in plants, where cell divisions occur for plant growth and also present in the middle lamellae of cells.

• During telophase, the nucleolus, ER and Golgi apparatus reappears.
  
• During nuclear membrane and nucleolus reappears. daughter nuclei formation takes place.

Meiosis I begins with diploid (2n=4) cell and ends with two haploids (n = 2) cells. In humans ( 2n=46), who have 23 pairs of chromosomes, the number of chromosomes is reduced by half at the end of meiosis. I (n=23).

• Correlating the question with the image above, D represents the synthetic phase. 
• It occurs between the G1 and G2 phases of the cycle. The actual duplication of the genome takes place during this phase and is highly regulated. 

After mitosis, the cell enters the G1 or the growth phase and then continues with DNA synthesis in the S phase which is followed by the G2 phase.

A. Anaphase – Contraction of spindle fibres takes place, division of centromere occurs, daughter chromosomes move towards the poles.

B. Prophase – condensation of chromosomes occur. Chromosomes thick, short.

C .Metaphase – Metaphasic or equatorial plate is formed.

D. Telophase – Decondensation of chromosomes takes place. Chromosome elongated and their length increases.

So, the correct option is ‘Telophase’.

The correct answer is $$(A)$$.

Wheat is an angiosperm plant. In this plant $$80$$ grains (seeds) are produced by fertilization between $$80$$ male and $$80$$ female gametes. $$80$$ male gametes therefore, pollen grains are produced by $$20$$ meiosis in microspore mother cells while $$80$$ female gametes therefore, megaspores are formed by $$80$$ meiosis in megaspores mother cells because in angiosperm plants, after meiotic division in single megaspore mother cell, four megaspores are formed but only one megaspore is survived and other three get degenerated. Thus total meiotic divisions are $$20 + 80 = 100$$.

So, the correct option is '100'.

During the S phase or synthetic phase of interphase, replication of DNA and synthesis of histone proteins occur. New histones are required in massive amounts immediately at the beginning of the S period of DNA synthesis to provide the new DNA with nucleosomes.