Question

Give the name of the phases of meiosis, in which
I. the chromosome number is reduced to a haploid state.
II. the amount of DNA is reduced to haploid state.
A. Anaphase-II, Anaphase-I
B. Anaphase-I, Metaphase-II
C. Anaphase-I, Anaphase-II
D. Anaphase-II, Metaphase-I

Answer 1

Hint: In higher organisms, two types of cells are present in the body which are somatic cells and the germinal cells. The germinal cells are haploid cells that are produced through a division which reduces the number of chromosomes and this type of division is called as meiotic division.

Complete step by step answer: The meiosis type of cell division is known as the reductional cell division. It involves two different steps of complete cell division and gives rise to four daughter cells which are haploid. The four cells receive only a single copy of the parental chromosomes. The process of meiosis is important as it allows for mixing and crossing over and helps to create the new genetic recombination.
In meiosis, DNA replication takes place in the S phase which quickly follows the first meiotic division and then second meiotic division. Meiosis can be divided into two phases which are meiosis I and meiosis II. Both the phases are further divided into cytokinesis and karyokinesis. The interphase is the preparatory phase and is divided into two Growth phases and a Synthetic phase. Interphase is then followed by meiosis I and then meiosis II.
In the meiosis I phase, the homologous chromosomes get separated and are joined as tetrads. THe first phase is the prophase I and, in this phase, pairing between the homologous chromosomes takes place. The paired and replicated chromosomes are called tetrads and contain two chromosomes and four chromatids. In metaphase I, the tetrads move to the equatorial plate. During the anaphase I stage, the tetrads are pulled towards the pole and kinetochore microtubules are shortened. THe centromere is pushed farther apart. It is in this phase, the chromosome number is reduced to haploid as the daughter chromatids are pulled to opposite ends. The next phase is telophase stage and the chromosomes arrive at the two opposite poles. Each of the daughter cells now contains half the number of chromosomes but the chromosomes consist of a pair of chromatids.
The second part of the division is known as the meiosis II and it is the equational segregation or the separation of the sister chromatids. In prophase II, the shortening and thickening of the chromatids takes place and the centrosomes move to the poles. In metaphase II, the centromeres containing the two kinetochores which attach to the spindle fibers move to the opposite poles. This step is followed by the anaphase II and the sister chromatids segregate and move towards the opposite poles. It is in this phase, the DNA is reduced to half. This stage moves onto the next phase which is the telophase II and it shows decoiling and lengthening of chromosomes followed by disassembly of the spindle. The nuclear envelope starts forming and four daughter cells are formed.
Therefore, the correct option is option C.

Note: The meiosis is the reductional division and it gives rise to four daughter cells. The four daughter cells are haploid and contain half the number of chromosomes. The anaphase I stage is the phase where the chromosomes are reduced into half or haploid state.