
Which one of the following processes results in the production of recombinants in future generations?
(i) Mutation
(ii) Independent assortment during meiosis I.
(iii) Independent assortment during meiosis II.
(iv) Crossing over of bivalents.

Important Questions on Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.




Fill in the blank with the most appropriate option given below.
We should give everyone training in citizenship, but we have______this aspect till now.




Match the changes which occur in the chromosomes during meiosis, with the different phases of prophase-I.
List - I | List - II | ||
(a) | Pachytene | (i) | Compaction of chromosomes |
(b) | Zygotene | (ii) | Terminalisation of chiasmata |
(c) | Diplotene | (iii) | Pairing of chromosomes |
(d) | Leptotene | (iv) | Dissolution of synaptonemal complex |
(v) | Recombination nodule |
The correct answer is

Assertion In crossing over, the exchange of genetic material between two homologous chromosomes occur during both mitotic and meiotic cell divisions.
Reason The process of crossing over is only possible and is mediated by recombinase.
The correct answer is:


I | II | ||
() | Synapsis aligns homologous chromosomes | () | Anaphase – II |
() | Synthesis of RNA and protein | () | Zygotene |
() | Action of enzyme recombinase | () | – phase |
() | Centromeres do not separate but chromatids move towards opposite poles | () | Anaphase – I |
() | Pachytene |






Pair of homologous chromosomes
Tetrad of chromatids
Bivalent chromosomes
Recombination modules of non sister chromatids

Column-I | Column–II | ||
a. | Pachytene | (i) | The pairing of homologous chromosomes |
b. | Metaphase I | (ii) | Terminalization of chiasmata |
c. | Diakinesis | (iii) | Crossing-over takes place |
d. | Zygotene | (iv) | Chromosomes align at the equatorial plate |

i. Crossing over
ii. Synapsis
iii. Terminalisation of chiasmata
iv. Disappearance of the nucleolus

