DIRECTIONS for Q.44 : Given question contain STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has 4 choices (a), (b), (c) and (d) out of which ONLY ONE is correct.
Statememt 1 : Chiasmata is formed during diplotene.
Statememt 2 :Chiasmata are formed due to deposition ofnucleoproteins.

Statement- 1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement -1
Statement -1 is True, Statement -2 is True ; Statement-2 is NOT a correct explanation for Statement - 1
Statement - 1 is True, Statement- 2 is False
Both the Statements are False.44.

Solution

The points of attachment between the homologous chromosomes after the partial dissolution of nucleoprotein complex are called chiasmata. It occurs during diplotene substage of prophase I.

Which one is correct about bivalent ?
(1)Bivalent are tetrads.
(2)A bivalent means 4 chromatids and 2 centromere.
(3)One bivalent consists of 2 homologous chromosomes each and sister chromatids.
(4)Bivalents form in zygotene.

All are correct
Only 3
3 and 4
Only 4

Four different steps that occur during meiosis are given in the following list.
(1)Complete separation of chromatids.
(2)Pairing of homologous chromosomes.
(3)Lining up of paired chromosomes on equator.
(4)Crossing over between chromatids. These steps would occur in the order-

2, 3, 4, 1
3, 2, 4, 1
2, 4, 3,1
3, 1, 2, 4

Which one is correct for G_zero stage ?
(1)It is a quiescent stage.
(2)In this phase cell cycle is stopped.
(3)G_zero cells do not grow or proliferate but metabolically active.(4)G_zero cells can divide in response to some stimulus.

All are correct
1, 2, 3 are correct
1, and 2 are correct
Only 1 and 4 are correct

A cell in prophase of mitosis can be distinguished from a cell in prohase-I of meiosis by

The presence of only half as many chromosomes in the meiotic cell
The formation of tetrads in the meiotic cell
The presence of twice as many chromosomes in the meiotic cell
None of the above

All cells of a multi cellular body have same karyotype because the body has developed from azygote by –

meiotic and mitotic divisions
only mitotic divisions
only meiotic divisions
mitotic and amitotic divisions

Crossing over during meiosis occurs at four strand stage. This is proved by the observation that

rarely all four gametes resulting from a meiotic division could be recombinants
usually only two gametes resulting from meiotic division could be recombinants
chaismata are seen only at the four strand stage.
occasionally none of the four gametes resulting from meiosis could be a recombinant.

Yeast cell divides once in aproximately every –

90 minutes
9 minutes
24 hours
24 days

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