Question

Choose the correct statements regarding cytology of haploids -
A. A haploid in Arabidopsis will have 5 chromosomes.
B. Haploids are found as bivalents at metaphase-I of meiosis.
C. Haploids are found as univalent at metaphase-I of meiosis.
D. The haploids in maize will have 10 chromosomes.
E. The haploids in maize will have 20 chromosomes.
Choose the correct answer from the options given below :

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

Hint:

Meiosis in haploids is abnormal because there are no homologous chromosomes to form pairs (bivalents). Chromosomes remain as univalents, leading to irregular segregation and sterility.

Answer 1

The Correct Option is C

Step 1: Concept Overview:
This question assesses understanding of chromosome number and meiotic behavior in haploid organisms, using Arabidopsis and maize as examples. A haploid organism possesses a single set of chromosomes (\(n\)).
Step 2: Detailed Analysis:
A. Arabidopsis haploids have 5 chromosomes. Arabidopsis thaliana, a diploid model plant, has \(2n = 10\) chromosomes. Therefore, its haploid gamete (or a haploid plant) contains \(10/2 = 5\) chromosomes. (Correct)
B. Haploids form bivalents at metaphase-I of meiosis. A bivalent consists of a pair of synapsed homologous chromosomes. Haploids, having only one set of chromosomes, lack homologous partners, preventing bivalent formation. (Incorrect)
C. Haploids form univalents at metaphase-I of meiosis. During meiosis in a haploid cell, each chromosome lacks a homolog to pair with, remaining as a single, unpaired chromosome termed a univalent. (Correct)
D. Maize haploids have 10 chromosomes. Diploid maize (Zea mays) has \(2n = 20\) chromosomes. Consequently, a haploid cell or plant will have \(n = 10\) chromosomes. (Correct)
E. Maize haploids have 20 chromosomes. 20 represents the diploid (\(2n\)) chromosome number in maize, not the haploid number. (Incorrect)
Step 3: Conclusion:
Statements A, C, and D are correct.