Find out the correct sequence in decreasing order of chromosome number of the following
(A) Egg cell of Zea mays
(B) Microspore of Oryza sativa
(C) Synergid of Allium cepa
(D) Secondary nucleus of Pisum sativum

Options

A. DBAC
B. DABC
C. BDAC
D. CADB

Answer

To find the correct sequence in decreasing order of chromosome number for the given cells, we will analyze each option step by step.

### Step 1: Determine the chromosome number for each cell type.

**(A) Egg cell of Zea mays:**
- Zea mays (corn) has a diploid chromosome number (2N).
- The haploid number (N) for Zea mays is 10.
- Therefore, the diploid number is:
\[ 2N = 2 \times 10 = 20 \]

**(B) Microspore of Oryza sativa:**
- Oryza sativa (rice) also has a diploid chromosome number (2N).
- The haploid number (N) for Oryza sativa is 12.
- Therefore, the diploid number is:
\[ 2N = 2 \times 12 = 24 \]

**(C) Synergid of Allium cepa:**
- Allium cepa (onion) has a diploid chromosome number (2N).
- The haploid number (N) for Allium cepa is 8.
- Therefore, the diploid number is:
\[ 2N = 2 \times 8 = 16 \]

**(D) Secondary nucleus of Pisum sativum:**
- Pisum sativum (pea) has a triploid structure in the secondary nucleus.
- The haploid number (N) for Pisum sativum is 12.
- Therefore, the triploid number is:
\[ 3N = 3 \times 12 = 36 \]

### Step 2: List the chromosome numbers obtained.
- (A) Egg cell of Zea mays: 20
- (B) Microspore of Oryza sativa: 24
- (C) Synergid of Allium cepa: 16
- (D) Secondary nucleus of Pisum sativum: 36

### Step 3: Arrange the chromosome numbers in decreasing order.
- D: 36
- B: 24
- A: 20
- C: 16

### Final Sequence:
The correct sequence in decreasing order of chromosome number is:
**D (36), B (24), A (20), C (16)**