1. It is commonly used for transferring a single gene from a donor to a recurrent parent. 

2. It is effective only when the trait is governed by multiple genes. 

3. It is useful for eliminating undesirable traits linked with the donor genotype. 

4. It involves repeated crossing of F1 with the donor parent. 

Which of the above statements are correct? 

A. 1, 2 and 3 

B. 1 and 3 only 

C. 1, 3 and 4 

D. 2, 3 and 4 


Correct Answer: B. 1 and 3 only

Explanation:

  1. Correct – The back-cross method is commonly used to transfer a specific gene from a donor parent to an adapted recurrent parent.

  2. Incorrect – It is particularly effective for transferring traits governed by one or a few major genes, rather than only polygenic traits.

  3. Correct – Selection during backcrossing helps recover the desirable characteristics of the recurrent parent while retaining the target gene. However, undesirable linked genes may require additional selection or recombination to eliminate.

  4. Incorrect – The F₁ and subsequent selected progenies are repeatedly crossed with the recurrent parent, not the donor parent.

Key exam point: Backcrossing = recurrent parent × selected progeny to transfer a desired trait while recovering the recurrent parent's genetic background.