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: Understanding the Concept:
The question tests knowledge about the chromosome number and meiotic behavior of haploid organisms, using Arabidopsis and maize as examples. A haploid organism has a single set of chromosomes (\(n\)).
Step 2: Detailed Explanation:
A. A haploid in Arabidopsis will have 5 chromosomes. The model plant Arabidopsis thaliana is a diploid with \(2n = 10\) chromosomes. Therefore, its haploid (\(n\)) gamete or a haploid plant would have \(10/2 = 5\) chromosomes. (Correct)
B. Haploids are found as bivalents at metaphase-I of meiosis. A bivalent is a pair of synapsed homologous chromosomes. Since haploids have only one set of chromosomes, they lack homologous partners. Thus, bivalents cannot be formed. (Incorrect)
C. Haploids are found as univalent at metaphase-I of meiosis. In a haploid cell undergoing meiosis, each chromosome has no homolog to pair with, so it remains as a single, unpaired chromosome, which is called a univalent. (Correct)
D. The haploids in maize will have 10 chromosomes. Diploid maize (Zea mays) has \(2n = 20\) chromosomes. Consequently, a haploid cell or plant will have \(n = 10\) chromosomes. (Correct)
E. The haploids in maize will have 20 chromosomes. 20 is the diploid (\(2n\)) chromosome number for maize, not the haploid number. (Incorrect)
Step 3: Final Answer:
The correct statements are A, C, and D.