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

DNA replication in bacteria occurs

(1) during S-phase

(2) within nucleolus

(3) prior to fission 

(4) just before transcription 

Anaphase promoting complex (APC) is a protein degradation machinery necessary for proper mitosis of animal cells. If APC is defective in a human cell, which of the following is expected to occur?

(1) Chromosomes will not condense

(2) Chromosomes will be fragmented

(3) Chomosomes will not segregate

(4) Recombinantion of chromosome arms will occur