There are three genes a, b, c, percentage of crossing over between a and b is 20%, b and c is 28% and a and c is 8%. What is the sequence of genes on chromosome?

Options

A. b, a, c
B. a, b, c
C. a, c, b
D. None of these

Explanation

To determine the sequence of genes A, B, and C based on the given percentages of crossing over, we can follow these steps:

### Step 1: Understand the Crossing Over Percentages
We have the following percentages of crossing over:
- Between A and B: 20%
- Between B and C: 28%
- Between A and C: 8%

### Step 2: Analyze the Percentages
The percentage of crossing over indicates how far apart the genes are on a chromosome. A lower percentage means that the genes are closer together, while a higher percentage indicates that they are further apart.

### Step 3: Identify Closest Genes
From the percentages:
- A and C have the lowest crossing over percentage (8%), indicating they are the closest genes.
- A and B have a crossing over percentage of 20%.
- B and C have the highest crossing over percentage (28%), indicating they are the most distant.

### Step 4: Arrange the Genes
Since A and C are the closest, we can place them next to each other. Now we need to place B:
- Since A and C are closest, we can write them as A - C.
- B has a higher crossing over percentage with both A and C, but it is closer to A than C based on the crossing over percentages.

Thus, the sequence of genes can be arranged as:
- A - B - C

### Step 5: Confirm the Sequence
To confirm:
- The distance between A and C is the shortest (8%).
- The distance between A and B is 20%.
- The distance between B and C is the longest (28%).

This confirms that the sequence of genes is indeed A, B, C.

### Final Sequence
The sequence of genes on the chromosome is: **A - B - C**.

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