Test: Meiosis (NCERT) - NEET MCQ

In diplotene stage of meiosis I, the chromosomes may unfold to nearly form and start transcription of mRNA and rRNA to build up food reserves in the cytoplasm. This process is most pronounced in the primary oocytes of amphibians, reptiles and birds. In some species, the chromosomes enlarge greatly, assuming lampbrush form.

Meiosis is the type of cell division by which gamete cells (eggs and sperm) are produced. Meiosis involves two successive nuclear divisions and one cytoplasmic division that produce four haploid cells. The first division (meiosis 1) is the reductional division during which number of chromosomes is reduced to half. The second division (meiosis II) separates the chromatids. It is called equational division as chromosome number remains the same as produced after meiosis-l.

Leptotene also known as leptonema is the first stage of prophase I during which individual chromosomes begin to condense into long strands within the nucleus which are loossely interwoven. However, the two sister chromatids are still so tightly bound that they are indistinguishable from one another. They possess a string of swollen areas called chromomeres.

Cytokinesis is the division of the cell's cytoplasm, which occurs after the nucleus has divided (mitosis or meiosis). This process ensures that the cytoplasmic contents and organelles are evenly distributed between the two daughter cells, completing the cell division process. In animal cells, cytokinesis is achieved through the formation of a cleavage furrow that pinches the cell into two. In plant cells, a cell plate forms to divide the cell. Cytokinesis is essential for the physical separation of the daughter cells.

The assertion is true because mitosis results in two daughter cells each having the same number of chromosomes as the parent cell, maintaining the species' specific chromosome number. The reason correctly explains the assertion because the single round of DNA replication before the cell division ensures that each daughter cell receives an exact copy of the parent cell's genome.

A characteristic feature of telophase is the re-formation of the nuclear envelope around the chromosomes at each pole of the cell. This phase marks the end of the nuclear division process, with the chromosomes beginning to decondense and return to their less compact chromatin state. Telophase sets the stage for cytokinesis, which will physically divide the cell into two daughter cells.

All the stages are of the meiosis 1 because here we can see the bivalent or tetrad stages. Metaphase is the stage where chromosome comes on the equator and bivalent arrange themselves on the equatorial plate. Then anaphase 1 involves the separation of a homologous chromosome which start moving up to opposite poles and each tetrad is divided into two daughter cells. So anaphase involves the production of chromosome number and is also known as disjunction. Telophase 1 shows the formation of two daughter nuclei but the chromosome number is half then the chromosome number of mother cell and nuclear membrane reappears.

Meiosis of one Pollen Mother Cell (PMC) produces 4 haploid pollen grains. Thus, for producing 1200 pollen grains 1200/4=300 PMCs are required.

During anaphase of mitosis, each chromosome arranged at metaphase plate is split and two daughter chromatids are formed. Centromeres split and chromatids move to opposite poles. During anphase I of meiosis I, the homologous chormosomes separate, while sister chromatids remain associated at their centromeres. Anaphase II of meiosis II begins with simultanoeus splitting of the centromere of each chromosome allowing them to move towards oppostie poles of the cell.

Meiosis I consists of separation of the homologous chromosomes, each made up of two sister chormatids into two cells. Entire haploid content of chomosomes is contained in each of the resulting daughter cells. The first meiotic division therefore reduces the ploidy of the original cell by a factor of 2. Meiosis II consists of decoupling of each chormosome sister strands (chromatids) and segregating the individual chromatids into haploid daughter cells. The two cells resulting from meiosis I divide during meiosis II, creating 4 haploid daughter cells.

During pachytene sub-stage of meiosis I, crossing over i.e. exhcnage of genetic material takes place between homologous, which results in recombinations. The two homologous chromosomes are contributed by different parents. One of them is partnerl chromosome and the other one is maternal chormosome.

Homologous chormosomes are chormosomes having same structural features. In dipilod nuclei, pairs of homologous chromosomes can be identified at the start of meiosis. One member of each pair comes from the female parent and other from the male parent. Homologous chromosomes have the same pattern of genes along the chromosome but the nature of the genes may differ.

The alignment of chromosomes at the metaphase plate does not occur during prophase of mitosis. This event occurs during metaphase, the stage following prophase. Prophase is characterized by the condensation of chromatin into visible chromosomes, the breakdown of the nuclear envelope, and the beginning of the formation of the mitotic spindle.

The G₂ phase of the cell cycle is a period of rapid cell growth and protein synthesis, during which the cell prepares for mitotic division. This phase follows DNA replication in the S phase and precedes the M phase (mitosis), ensuring that the cell has all the necessary components for successful division.

Pairing of homologous chromosomes occurs in zygotene and crossing over occurs in pachytene stage of prophase I of meiosis I. Paired chromosomes line up on equator in metaphase I. Then there is complete separation of chromatids in anaphase I of meiosis I.

Meiosis is a double division that occurs in the reproductive cell in which nucleus divide but chromosome replicate only once to form four haploid cells, each cell having half the number of chromosomes present in a parent cell. It causes a reduction in the number of chromosomes. It is also known as reduction division. Meiosis in a cell occurs only once to form gametes.

Metaphase is characterized by the alignment of chromosomes at the cell's equator, also known as the metaphase plate. This alignment ensures that each daughter cell will receive an equal and identical set of chromosomes when the chromosomes are pulled apart in the subsequent anaphase.

The homologous chromosomes break their connections and separate out during anaphase I of meiosis I. This process of separation is named as disjunction.

Anaphase II, where the centromeres are cleaved, allows the kinetochores to pull the sister chromatids apart. The sister chromatids by convention are now called sister chromosomes and they are pulled towards opposte poles.

• Meiosis is divided into two stages- meiosis I and meiosis II.
• In each stage, the cell undergoes separation of chromosomes during anaphase I and anaphase II, cytokinesis and karyokinesis.