Question

Gene A, B, and C are located on the same chromosome. Test crosses show that the recombination frequency between A and B is 28% and that between A and C is 12%. Can you determine the linear order of these genes?

Short answer

There are two possibilities of arranging the genes, such as A-C-B or C-A-B. It is difficult to determine the linear order without the recombination frequency between B and C being predicted.

Step-by-step solution

Definition of gene and chromosome

The portion of DNA that is coding for a particular protein is known as a gene. The chromosomes are the linear structure that is composed of DNA and protein-bound towards each other.

Description of recombination frequency

In two genes, the frequency that corresponds to the single chromosome cross is known as recombination frequency. The unit of recombination frequency is the centimorgan. It is denoted by the symbol of θ.

Prediction of recombinant frequency in the gene A, B, and C.

The recombination frequency of test crosses between the gene A and B is 28%. The recombination frequency of the other two genes, A and C, is 12%.

The linear order of gene arrangement can take place in two ways, such as A-C-BorC-A-B. It is difficult to predict the exact linear formation formed from these two combinations. It is necessary to know the recombination frequency of another pair, such as B and C.

Hence, the recombination frequency of another pair, such as B and C, is necessary to determine the linear order of the genes.