Which genotype ratio will appear by the trihybrid test cross in a completely linked plant :-

Options

A. `1 : 1 : 1 : 1 : 1 : 1 : 1 : 1`
B. `1 : 1 : 1 : 1`
C. `1 : 1`
D. `1 : 2 : 1`

Answer

To solve the question regarding the genotype ratio that will appear from a trihybrid test cross in a completely linked plant, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Trihybrid Cross**:
A trihybrid cross involves three different traits. Each trait is determined by a pair of alleles. For example, let’s consider three traits:
- Trait 1: Round (R) vs. Wrinkled (r)
- Trait 2: Green (Y) vs. Yellow (y)
- Trait 3: Smooth (C) vs. Constricted (c)

2. **Identifying Alleles**:
In a completely linked scenario, the alleles for these traits are inherited together without any recombination. This means that the alleles will stay together as they are on the same chromosome.

3. **Genotype of Parents**:
For a test cross, one parent will be homozygous recessive for all traits (rryycc), while the other parent will be heterozygous for all traits (RrYyCc).

4. **Gametes Formation**:
Since the genes are completely linked, the heterozygous parent can only produce one type of gamete: RYc. The homozygous recessive parent can only produce one type of gamete: ryc.

5. **Offspring Genotypes**:
When we perform the test cross, the offspring will inherit the alleles as follows:
- From RrYyCc (heterozygous): RYc
- From rryycc (homozygous recessive): ryc

Therefore, all offspring will have the genotype RrYyCc.

6. **Genotype Ratio**:
Since all offspring are genetically identical due to complete linkage, the genotype ratio will be 1:1:1, which means all offspring will express the dominant traits.

### Conclusion:
The genotype ratio that will appear from a trihybrid test cross in a completely linked plant is **1:1:1**.