Question

Choose the correct statements regarding homozygous diploid plants -
A. They are produced by doubling the chromosome number of haploids.
B. Doubling of chromosome enables the recessive traits to express too.
C. Chromosome doubling is done by Ozone treatment.
D. Chromosome doubling is done by colchicine treatment.
Choose the correct answer from the options given below:

• A. A, B and D Only
• B. A, C and D Only
• C. A, B and C Only
• D. A, and D Only

Hint:

Associate {Colchicine} with {Chromosome doubling}. It's a classic tool in plant breeding to induce polyploidy and create homozygous lines from haploids.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The question is about the production and characteristics of "doubled haploids," which are homozygous diploid plants used in plant breeding.
Step 2: Detailed Explanation:
A. They are produced by doubling the chromosome number of haploids. This is the definition of a doubled haploid. Haploid plants (n) are first produced via anther or ovule culture, and then their chromosome set is doubled to create a completely homozygous diploid (2n) plant. (Correct)
B. Doubling of chromosome enables the recessive traits to express too. In a haploid organism, every gene (including recessive alleles) is expressed because there is no other allele to mask it. When the chromosomes are doubled (e.g., a haploid with allele 'r' becomes a diploid 'rr'), the recessive trait remains expressed and is now fixed in a homozygous state. (Correct)
C. Chromosome doubling is done by Ozone treatment. Ozone is a strong oxidizing agent used for sterilization, not for inducing polyploidy. This statement is (Incorrect).
D. Chromosome doubling is done by colchicine treatment. Colchicine is a chemical extracted from the autumn crocus. It is a mitotic inhibitor that disrupts the formation of the spindle fibers during cell division. This prevents the separation of chromosomes, leading to a doubling of the chromosome number in the cell. This is the standard method used for producing doubled haploids. (Correct)
Step 3: Final Answer:
Statements A, B, and D are correct.