In which one of the following combinations (1-4) of the number of chromosomes is the present day hexaploid wheat correctly represented ?

Options

A. (a) `{:("Combination","Mosomic","Haploid","Nullisomic","Trisomic"),(,21,28,42,43):}`
B. (b) `{:("Combination","Mosomic","Haploid","Nullisomic","Trisomic"),(,7,28,40,42):}`
C. (c) `{:("Combination","Mosomic","Haploid","Nullisomic","Trisomic"),(,21,7,42,43):}`
D. (d) `{:("Combination","Mosomic","Haploid","Nullisomic","Trisomic"),(,41,21,40,43):}`

Answer

To determine the correct representation of the present-day hexaploid wheat in terms of chromosome combinations, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Hexaploid Wheat**: Hexaploid wheat has six sets of chromosomes. The scientific name for this wheat is *Triticum aestivum*.

2. **Identify the Basic Chromosome Number**: The basic chromosome number (x) for wheat is 7. Therefore, for hexaploid wheat (6x), the total number of chromosomes is calculated as:
\[ \text{Total Chromosomes} = 6 \times 7 = 42 \]

3. **Determine the Haploid Number**: The haploid number (n) is half of the diploid number. For hexaploid wheat:
\[ n = \frac{42}{2} = 21 \]

4. **Analyze Chromosomal Conditions**:
- **Monosomic Condition**: This condition occurs when one chromosome is missing. Therefore, the total number of chromosomes would be:
\[ 42 - 1 = 41 \]
- **Nullisomic Condition**: This condition occurs when a pair of chromosomes is missing. Therefore, the total number of chromosomes would be:
\[ 42 - 2 = 40 \]
- **Trisomic Condition**: This condition occurs when one extra chromosome is present. Therefore, the total number of chromosomes would be:
\[ 42 + 1 = 43 \]

5. **Evaluate the Options**: Now, we need to check the options provided in the question to find which one corresponds to the haploid number (n = 21) or any of the other conditions (monosomic, nullisomic, trisomic):
- **Haploid (n = 21)**: 21
- **Monosomic (2n - 1)**: 41
- **Nullisomic (2n - 2)**: 40
- **Trisomic (2n + 1)**: 43

6. **Select the Correct Option**: From the analysis, we find that the only option that correctly represents the haploid condition (n = 21) is option D.

### Conclusion:
The correct combination of the number of chromosomes representing present-day hexaploid wheat is **Option D**.

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