Question

Rina is studying the inheritance of stem height and stem color where the tall and brown phenotype is dominant over short and green. She mated a purebred tall, brown plant to a purebred short, green plant and all of the F${}_1$ offspring are tall and brown. On selfing of F${}_1$ generation, she observed following phenotypes in F${}_2$ offspring: 61 tall and brown, 1 tall and green, 2 short and brown, and 18 short and green. Which of the following will be true?

• A. The two genes controlling these traits are sex linked.
• B. The two genes controlling these traits might be on different chromosomes.
• C. The two genes controlling these traits are linked with no crossing over.
• D. The two genes controlling these traits are nearby on the same chromosome.
• E. The two genes controlling these traits are far apart on the same chromosome.

Answer 1

The correct option is D The two genes controlling these traits are nearby on the same chromosome.

Genetic linkage is the tendency of the DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. The nearer the two genes are on a chromosome, the lower the chances of recombination i.e. more of the parental characters are inherited.

In the given example, F${}_2$ offspring have more of parental characters than recombinants. A large number of offsprings possess tall and brown characters (dominant parent) as compared to short and green (recessive parents).

Therefore, in this experiments the offsprings linkage which proved that the genes for the characters were present very close to each other.

So, the correct option is 'The two genes controlling these traits are nearby on the same chromosome'.