Question

1. Figure 4.1 shows the names of different stages that occur during meiosis.

anaphase I	metaphase II	anaphase II
telophase II	prophase I	metaphase I

Figure 4.1

Using the stages in Figure 4.1, state the stage(s) in which the following events occur:

1. independent assortment. [1]
2. formation of the spindle apparatus. [1]
3. separation of sister chromatids. [1]
4. formation of nuclear membranes. [1]
5. chromosomes pulled to opposite poles. [1]

Answer 1

Ans) a) Independent reassortment- Metaphase-I

(Independent reassortment occurs during Metaphase-I stage of Meiosis-I during which random segregation of chromosomes occur i.e Chromosome from father and from mother can be segregated either to left or right side of the cell and because of this random segregation, different combination of alleles is possible).

b) Formation of spindle apparatus - Prophase-I

(Formation of spindle apparatus occurs at Prophase-I stage of Meiosis-I which is a pre requisite because during the metaphase stage,the chromosomes are aligned at the equatorial plate).

c) Separation of sister chromatids - Anaphase-II

(Sister chromatids are separated during anaphase-II of Meiosis-II wheras homologous chromosomes are separated during Anaphase-I of Meiosis-I).

d) Formation of nuclear membranes - Telophase-II

(Nuclear membranes form around the chromosomes and the chromosoems will decondense during the telophase stage)

e) Chromosomes pulled to opposite poles - Anaphase-I

(Homologous chromosomes are separated during Anaphase-I stage of Meiosis-I wheras sister chromatids are separated during Anaphase-II stage of Meiosis-II)