Question

The points of crossing over in meiosis appear as
(a) Synaptonemal complexes
(b) Protein axes
(c) Chiasmata
(d) Diakinesis

Answer 1

Meiosis occurs in two steps and leads to the reductional division where the chromosome number divides into half of the original. Crossing over takes place at the pachytene stage but the mark of crossing over takes place in the next stage where paired chromosomes are bivalent, short and thick.

Complete answer:
In the diplotene stage nucleoprotein fuse and the synapsed chromosome get dissolved which cause separation of homologous chromosome leaving the point where crossing over takes place, due to this the chromatids become very clear by forming the tetrads. The point of attachment between homologous chromosomes after the partial dissolution of the nucleoprotein complex called chiasmata. The chiasmata mark sites of crossing over which may be terminal or interstitial. Depending upon the position of the site of crossing over the structure of the chromosome gets formed. This structure changes with the stages and sometimes disappears.
In oocytes, diplotene lasts for many months and sometimes for a year, at this interval the chromosome decondensed and gets engaged in RNA synthesis and in some animals this chromosome expands, forming a lampbrush chromosome. After the diplotene stage, diakinesis starts with the disappearance of chiasmata toward the end of the chromosome which leads to Terminalisation by which the nucleolus and nucleoli disappear and the nuclear envelope gets to break down into vesicles.

So the correct answer is option c) Chiasmata.

Note:
The crossing over takes place at the pachytene stage, where the exchange of non-sister chromatids takes place at homologous chromosomes. This crossing takes place by breakage and reunion of chromatids segments and after the crossing over the two chromatids become dissimilar.