A) Leptotene
B) Zygotene
C) Pachytene
D) Diplotene
Correct Answer: C
Solution :
Pachytene or thick thread stage is the longest stage of prophase-I. During this stage, chromosomes contract longitudinally and they become shortened, thickened and coiled. Now the pairs of homologous chromosomes are called bivalent. Each bivalent has two chromatids by the middle of the pachytene stage as result of which, bivalent really consist of four chromatids and is called tetrad. During leptotene or leptonema or thin thread stage. Nucleus increases in size and chromosomes become more apparent as thin thread. During zygotene or zygonema, homologous chromosomes pair up and the phenomenon of pairing is called synapsis. Since each parent contributes a haploid set of chromosomes to a diploid offspring. All diploid cells are genetically similar. Diplotene or diplonema or double thread stage is recognized by the tendency of homologous chromosomes of the bivalent to pull away from each other.
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