Question

At the metaphase plate during metaphase 1 of meiosis, there are
A) Single chromosome
B) Bivalents
C) Always 23 chromosomes
D) Unpaired duplicate chromosome

Answer 1

Hint: Meiosis is the process of cell division that takes place in the reproductive cells. It occurs in two stages- Meiosis I and II. It is known as reductional division.

Complete answer:
To know about a stage in meiosis, we must first know the process of meiosis. For the process of sexual reproduction to occur, meiosis is a very important stage. It takes place in the reproductive organs. As the characteristic of meiosis is, we will obtain half the number of chromosomes in the gamete formed. Thus, the formation of haploid sperms is done in testes and of haploid ova is done in the ovaries.

In flowering plants, the formation of haploid gametes is done in anther and ovule . Meiosis involves two divisions of the cell. These two divisions are termed meiosis 1 and meiosis 2. Each one include prophase, metaphase, anaphase and telophase .

The prophase of first meiotic division, includes five more phases namely – leptotene, zygotene, pachytene, diplotene and diakinesis. In the zygotene stage, a complex is formed by a pair of synapses homologous chromosome called a bivalent or a tetrad.

This continues in the metaphase 1 stage. In this stage, the homologous chromosomes arrange themselves in an equatorial line.These homologous pairs are known as bivalents. The arms of chromosome face the equatorial plate while the centromere is assigned on opposite poles.

The diagram below represents the different stages of Meiosis 1.

Now from the above discussion we know that at the metaphase plate during metaphase 1 of meiosis, there are bivalent chromosomes and so option (C) is our right answer.

Note: At the metaphase, the chromosomes condense and are visible. In this stage the chromosomes align themselves in pairs at the centre so that the complete copies of chromosomes are there in both the daughter cells obtained after meiosis I.