During cell growth, DNA synthesis takes place in

(1) S-phase                       

(2) ${\mathrm{G}}_1$-phase

(3) ${\mathrm{G}}_2$-phase                     

(4) M-phase 

Spindle fibres attach on to 

1. Kinetochore of the chromosome

2. centromere of the chromosome

3. Kinetosome of the chromosome

4. telomere of the chormosome 

In meiosis crossing over is initiated at 

1. leptotene

2. Zygotene

3. diplotene

4. pachytene

During cell growth, DNA synthesis takes place in:

1. S-phase

2. G₁-phase

3. G₂ -phase

4. M-phase

Which of the following options gives the correct sequence of events during mitosis?