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

(1) Condensation → nuclear membrane disassembly → crossing over → Segregation → telophase

(2) Condensation → nuclear membrane disassembly → arrangement at equator → centromere division → Segregation → telophase

(3) Condensation → crossing over → nuclear membrane disassembly → Segregation → telophase

(4) Condensation → arrangement at equator → centromere division → Segregation → telophase

During cell growth, DNA synthesis takes place in

(1) S-phase                       

(2) ${\mathrm{G}}_1$-phase

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

(4) M-phase 

When cell has stalled DNA replication fork, which checkpoint should be predominantly activated?

(1) G₁/s

(2) G₂/M

(3) M

(4) Both G₂/M and M

Match the stage of meiosis in column I to their characteristic features in column II and select the correct option using the codes given below 
  Column l                                                 Column ll
A. pachytene                                1. pairing of homologous chromosomes

B. Metaphase-l                             2. Terminalisation of chiasmata

C. Diakinesis                                3. Crossing-over takes place
  
D. Zygotene                                 4. Chromosomes align at equatorial plate 

The correct option:

      A      B        C        D 
(1)  3      4        2        1
(2)  1      4        2        3
(3)  2      4        3        1
(4)  4      3        2       1   

A cell at telophase stage is observed by a student in a plant brought from the field. He tells his teacher that his cell is not like other cells at telophase stage. There is no formation of cell plate and thus the cell is containing more number of chromosomes as compared to other dividing cells. This would result in

(1) polyploidy

(2) somaclonal variation

(3) polyteny

(4) aneuploidy

Which of the following is not a characteristic feature during mitosis in somatic cells
1. Disappearance of nucleolus

2. Chromosome movement

3. Synapsis

4. Spindle fibres

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

A somatic cell that has just completed the S-phase of its cell cycle, as compared to gamete of the same species has

1. twice the number of chromosomes and twice the amount of DNA

2. same number of chromosomes but twice the amount of DNA

3. twice the number of chromosomes and four times the amount of DNA

4. four times the number of chromosomes and twice the amount of DNA

In S-phase of the cell cycle 

1. amount of DNA doubles in each cell

2. amount of DNA remains same in each cell

3. chromosome number is increased

4. amount of DNA is reduced to half in each cell