Cell Cycle and Cell Division Test - 48

Meiosis is important because it ensures that all organisms produced via sexual reproduction contain the correct number of chromosomes. Meiosis also produces genetic variation by way of the process of recombination.

Tetrads are formed in prophase I of meiosis I. Tetrad consist of two homologous chromosomes, each with two chromatids. Thus, a tetrad consists of 4 chromatids, two of which belong to each chromosome called sister chromatids which are joined at the centromere.

The cell cycle has three phases that must occur before mitosis. The three phases are collectively known as INTERPHASE. 

 Meiosis is a special type of cell division a process where a single cell divides two times to produce four haploid cells, each not only containing half the original amount of genetic information but also genetically distinct from the parent cell that gave rise to them. This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants and fungi.

For the first time, meiosis was discovered and described by Oscar Hertwig, a German biologist, in 1876, in sea urchin eggs. Then again in 1883, it was described by Edouard van Beneden in roundworms. A German biologist, August Weismann in 1890, described the significance of meiosis for reproduction and inheritance. The term "meiosis" was introduced by J.B. Farmer and J.E.S. Moore in the year 1905. Thus, the correct answer is option A. 

Meiosis occurs in two stages - meiosis I and meiosis II. The meiosis I is characterised by pairing of homologous chromosomes, crossing over and separation of homologous chromosomes. The centromere remains intact during meiosis I and homologous chromosomes separate. Thus, the number of chromosomes in progeny nuclei is reduced to one half. In meiosis II, just as mitosis, centromere separate and, hence, the number of chromosomes in the progeny remains same.

In a cell cycle the condensation of chromosome with visible centromere occurs during M-phase. 

Interphase, a phase of the cell cycle, is the one in which a cell spends most of its life. During this phase, the cell copies its DNA in preparation for mitosis. The cell obtains nutrients, uses them to grow and conducts other "normal" cell functions. It was previously known as the resting phase although the cell is preparing for cell division at a later stage. It is divided into three phases: 

1. G1 (first gap) - cell grows and functions normally. During G1, a large amount of protein synthesis occurs and the cell grows (to approximately double its original size) - a number of organelles are produced and the volume of the cytoplasm increases. 

2. S (synthesis) - the cell duplicates its DNA or synthesizes DNA. For replication of DNA, histone proteins are required. Therefore, they are also synthesized during this phase.

3. G2 (second gap) - the cell resumes its growth in preparation for division. 

The correct answer is option A.