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: Concept Overview:
This question concerns doubled haploids: homozygous diploid plants utilized in plant breeding.
Step 2: Detailed Analysis:
A. Production via Haploid Chromosome Doubling: Doubled haploids are created by duplicating the chromosome number of haploid plants. Haploids (n) are generated through anther or ovule culture, followed by chromosome doubling to yield a completely homozygous diploid (2n) plant. (Correct)
B. Recessive Trait Expression After Doubling: Haploid organisms express all genes, including recessive alleles, due to the absence of a masking allele. Chromosome doubling (e.g., 'r' becoming 'rr') fixes the recessive trait in a homozygous state, maintaining its expression. (Correct)
C. Chromosome Doubling via Ozone: Ozone, a strong oxidizing agent, is used for sterilization, not for inducing polyploidy. This statement is (Incorrect).
D. Chromosome Doubling via Colchicine: Colchicine, a chemical from the autumn crocus, is a mitotic inhibitor. It disrupts spindle fiber formation during cell division, preventing chromosome separation and causing chromosome number doubling. This is the standard method for producing doubled haploids. (Correct)
Step 3: Conclusion:
Statements A, B, and D are correct.