$ A cross between the pure recessive parent and the F-1 offspring is called Test cross.
! Test cross is a type of Back cross.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

To solve the question regarding the assertion and reason about test crosses and back crosses, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that a cross between a pure recessive parent and the F1 offspring is called a test cross.
- A test cross is specifically used to determine the genotype of an organism that exhibits a dominant phenotype.

2. **Defining the Test Cross**:
- A test cross involves crossing an individual with a dominant phenotype (which could be homozygous dominant or heterozygous) with a pure recessive individual (homozygous recessive).
- The purpose of this cross is to observe the phenotypes of the offspring to infer the genotype of the dominant parent.

3. **Analyzing the Results of a Test Cross**:
- If the dominant parent is homozygous dominant (AA), all offspring will display the dominant phenotype (100% dominant).
- If the dominant parent is heterozygous (Aa), the offspring will show a 1:1 ratio of dominant to recessive phenotypes (50% dominant and 50% recessive).

4. **Understanding the Reason**:
- The reason states that a test cross is a type of back cross.
- A back cross refers to the mating of an offspring with one of its parents or an individual genetically similar to its parent, which is aimed at preserving the parental genotype.

5. **Conclusion**:
- Both the assertion and the reason are true. The assertion correctly defines a test cross, and the reason correctly identifies it as a type of back cross.
- Therefore, the correct conclusion is that both the assertion and reason are correct, and the reason is the correct explanation for the assertion.

### Final Answer:
Both assertion and reason are correct, and the reason is the correct explanation for the assertion.

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