What proportion of offsprings are monohybrids in a dihybrid cross?

Options

A. `50%`
B. `25%`
C. `12.5%`
D. `6.25%`

Answer

To determine the proportion of offspring that are monohybrids in a dihybrid cross, we can follow these steps:

### Step 1: Understand the Ratios
In a monohybrid cross, the phenotypic ratio of the offspring is typically 3:1. This means that for every 4 offspring, 3 will show one trait and 1 will show the other trait.

In a dihybrid cross, the phenotypic ratio is 9:3:3:1. This means that for every 16 offspring, 9 will show both dominant traits, 3 will show the first dominant and the second recessive trait, 3 will show the first recessive and the second dominant trait, and 1 will show both recessive traits.

### Step 2: Calculate the Total Offspring
From the monohybrid cross, we have a total of 4 offspring (3 dominant + 1 recessive).
From the dihybrid cross, we have a total of 16 offspring (9 + 3 + 3 + 1).

### Step 3: Find the Proportion of Monohybrids
To find the proportion of monohybrids in a dihybrid cross, we need to compare the number of monohybrid offspring to the total number of offspring in the dihybrid cross.

The number of monohybrid offspring (from the 3:1 ratio) is 4 out of the total 16 from the dihybrid cross.

### Step 4: Calculate the Ratio
Now, we calculate the ratio of monohybrids to the total offspring:
\[ \text{Proportion of monohybrids} = \frac{\text{Number of monohybrids}}{\text{Total number of offspring}} = \frac{4}{16} = 0.25 \]

### Step 5: Convert to Percentage
To express this proportion as a percentage, we multiply by 100:
\[ 0.25 \times 100 = 25\% \]

### Final Answer
Thus, the proportion of offspring that are monohybrids in a dihybrid cross is **25%**.

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