Question

A cell with 16 chromosomes is treated with colchicine. How many chromosomes will the
cell have at the end? (Note: The chemical colchicine interferes with spindle formation.)
1. 32
2. 40
3. 16
4. 24

Answer 1

Correct Answer - Option 1 : 32

Concept:

• Poly means ''many'' and ploidy means '' haploid set of chromosomes'' so when a cell has three o sets of chromosomes then that condition is called polyploidy.
• Polyploidy in a cell can be induced by several methods like Colchine treatment, Heat or cold shock, and centrifugation.
• Polyploidy is of two types:

1. Autopolyploidy - It is the repetition of the same set of chromosomes. Eg - BBB
2. Allopolyploidy - Increase in both the types of genomes of a hybrid plant, formed from two different species. Using allopolyploidy new plant species can be formed. 

Explanation:

• Colchicine induces polyploidy in cells, as it interferes with spindle formation so the number of chromosomes doubles up after the treatment of colchicine.
• So when a cell with 16 chromosomes is treated with colchicine the number of chromosomes doubles up and it will have 32 chromosomes in the end.

• Use of Colchicine in plant breeding:
• Raphanobrassica (2n = 18) is obtained by crossing Raphanus sativus (2n = 18) and Brassica oleracea (2n = 18), which is a sterile plant, but after the application of colchicine the chromosome number doubles up and fertile Raphanabrassica (4n = 36) is formed.