In S–phase, DNA is replicated in a medium containing radioactive thymidine. Radioactivity will be observed in:
1.  Euchromatin
2.  Heterochromatin
3.  Both
4.  Nucleolus

What occurs in crossing over:
1.  Recombination
2.  Mutation
3.  Independent assortment
4.  None

Amount of cellular DNA increases during:

Spindle fiber unites with which structure of chromosomes:
1. Chromocenter
2. Chromomere
3. Kinetochore
4. Centriole

At which stage of the cell cycle does DNA replication occur:
1. G₁ - phase
2. S - phase
3. G₂ - phase
4. M - phase

The best material for the study of mitosis in the laboratory:

1. Anther

2. Root tip

3. Leaf tip

4. Ovary

If a diploid cell is treated with colchicine then it becomes:

1. Triploid

2. Tetraploid

3. Diploid

4. Monoploid

The cells of the quiescent centre are characterised by: 

1. Having dense cytoplasm and prominent nuclei

2. Having light cytoplasm and small nuclei

3. Dividing regularly to add to the corpus

4. Dividing regularly to add to tunica

Which one of the following precedes the reformation of the nuclear envelope during the M phase of the cell cycle:
 

Crossing over that results in genetic recombination in higher organisms occurs between:
1. Non-sister chromatids of a bivalent
2. Two daughter nuclei
3. Two different bivalents
4. Sister chromatids of a bivalent