Arrange the following in decreasing order based on the results obtained in the `F_(2)` progeny of dihybrid cross
(a) Total number of parental genotype
(b) Total number of recombinant genotypes
( c) Total phenotypes
(d) Total genotypes

Options

A. c,b,d,a
B. a,c,d,b
C. d,a ,c, b
D. d,b,c,a

Answer

To solve the problem of arranging the total number of parental genotypes, recombinant genotypes, phenotypes, and genotypes in decreasing order based on the results obtained in the F2 progeny of a dihybrid cross, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Total Number of Parental Genotypes**:
- In a dihybrid cross, there are typically two parental genotypes. For example, if we consider traits like round (R) vs. wrinkled (r) and yellow (Y) vs. green (y), the parental genotypes would be RRYY (round yellow) and rryy (wrinkled green).
- **Total Parental Genotypes = 2**

2. **Identify the Total Number of Recombinant Genotypes**:
- Recombinant genotypes arise from the combination of alleles that differ from the parental types. In a dihybrid cross, there are typically four recombinant genotypes.
- For example, if we cross RRYY with rryy, the recombinant genotypes would be RrYy, Rryy, rrYY, and rrYy.
- **Total Recombinant Genotypes = 4**

3. **Identify the Total Number of Phenotypes**:
- In a dihybrid cross, the phenotypic ratio is typically 9:3:3:1, resulting in four distinct phenotypes. For our example, the phenotypes would be round yellow, round green, wrinkled yellow, and wrinkled green.
- **Total Phenotypes = 4**

4. **Identify the Total Number of Genotypes**:
- The total number of genotypes in a dihybrid cross is 9. This includes all combinations of the alleles from both traits.
- For example, the genotypes would be RRYY, RRYy, RrYY, RrYy, RRyy, Rryy, rrYY, rrYy, and rryy.
- **Total Genotypes = 9**

5. **Arrange in Decreasing Order**:
- Now we have the following counts:
- Total Genotypes = 9
- Total Recombinant Genotypes = 4
- Total Phenotypes = 4
- Total Parental Genotypes = 2
- Arranging these in decreasing order:
- Total Genotypes (9) > Total Recombinant Genotypes (4) = Total Phenotypes (4) > Total Parental Genotypes (2)

### Final Arrangement:
- Total Genotypes (d) > Total Recombinant Genotypes (b) = Total Phenotypes (c) > Total Parental Genotypes (a)

### Conclusion:
The correct order based on the results obtained in the F2 progeny of a dihybrid cross is:
1. Total Genotypes (d)
2. Total Recombinant Genotypes (b)
3. Total Phenotypes (c)
4. Total Parental Genotypes (a)