Assertion(A): | Meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms. |
Reason(R): | Meiosis increases the genetic variability in the populations of organisms from one generation to the next. |
1. | Both (A) and (R) are true and (R) correctly explains (A) |
2. | (A) is true but (R) is false |
3. | (A) is false but (R) is true. |
4. | Both (A) and (R) are true but (R) does not correctly explain (A). |
1. | Zygotene | 2. | Pachytene |
3. | Diplotene | 4. | Leptotene |
1. | kinetochore |
2. | both centromere and kinetochore |
3. | centromere, kinetochore and areas adjoining centromere |
4. | centromere |
1. | Metaphase-spindle fibers attached to kinetochores, centromeres split and chromatids separate |
2. | Metaphase- chromosomes moved to spindle equator, chromosomes made up of two sister chromatids |
3. | Anaphase - centromeres split and chromatids separate and start moving away |
4. | Late prophase - chromosomes move to spindle equator |
I: | The complete disintegration of the nuclear envelope marks the start of metaphase. |
II: | Condensation of chromosomes is completed. |
III: | All the chromosomes come to lie at the equator. |
1. | Prophase II: | The nuclear membrane disappears by the end of this stage and the chromosomes again become compact. |
2. | Metaphase II: | The chromosomes align at the equator and the microtubules from opposite poles of the spindle get attached to the kinetochores of sister chromatids. |
3. | Anaphase II: | The homologous chromosomes separate, while sister chromatids remain associated at their centromeres. |
4. | Telophase II: | The two groups of chromosomes once again get enclosed by a nuclear envelope |
1. | At the end of the G1 phase |
2. | At the end of the S phase |
3. | At the end of Anaphase |
4. | In the resultant daughter cells |
1. | Two phases | 2. | Three phases |
3. | Four phases | 4. | Five phases |
Assertion(A): | Mitosis is called equational division. |
Reason(R): | The amount of DNA is the same in parent and progeny cells if it is mitosis. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true, but (R) is not the correct explanation of (A). |
3. | (A) is true, but (R) is false. |
4. | (A) is false, but (R) is true. |