Question

In a microscope , the number of chromosomes is 10 and DNA content is 20pg,what is the number of chromosomes and DNA content in its meiocyte at G1 Stage?
A) 20,20
B) 10,40
C) 20,40
D) 10,20

Answer 1

Hint: Meiosis is generally a type of cell division which is seen in sexually reproducing organisms to produce the sperm and egg cells.

Complete answer:
Meiosis is a particular type of cell division of germ cells in sexually-reproducing organisms used to produce the gametes, such as sperm or egg cells. It includes two rounds of division that eventually result in four cells with only one copy of each paternal and maternal chromosome .In addition, former to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, generating new combinations of code on each.

In meiosis, DNA replication is followed by two rounds of cell division to make four daughter cells, each with half the number of chromosomes as the original parent cell. The two meiotic divisions are generally known as meiosis I and meiosis II. Previous to meiosis begins, during the S phase of the cell cycle, the DNA of each chromosome is replicated as a result it consists of two identical sister chromatids, which stay held together through sister chromatid cohesion. Instantly following DNA replication, meiotic cells enter a prolonged G2-like stage known as meiotic prophase. At this time, homologous chromosomes pair with each other and undergo genetic recombination, a process in which DNA may be cut and then repaired, which allows them to switch over some of their genetic information.

During meiosis II, the unity between sister chromatids is released and they segregate from one another, as during mitosis. Meiosis produces haploid gametes ova or sperm that enclose one set of 23 chromosomes. When two gametes, an egg and a sperm, combine the resulting zygote is again diploid, with the mother and father each contributing 23 chromosomes. This identical pattern but not the same number of chromosomes, happens in all organisms that utilize meiosis.

A meiocyte is a type of cell that differentiates into a gamete during the process of meiosis. Throughout meiosis, the diploid meiocyte divides into four genetically different haploid gametes. The control of the meiocyte through the meiotic cell cycle varies among different groups of organisms.

Given that n = 10 and haploid DNA content is 20 pg, the meiocyte being diploid at G1 phase that is prior to S phase should contain 2n = 20 chromosomes and diploid DNA content that is 40 pg.

Hence the correct answer is option (C) 20, 40.

Note:Meiosis occurs in all the sexually reproducing single celled and multicellular organisms including animals, plants and fungi. It is an essential method for oogenesis and spermatogenesis.