In 1936 J. W. McKay crossed a stock melon plant that produced tan seeds with a plant that produced red seeds and got the following results:
tan seeds x red seeds à F1 13 tan seeds à F2 76 tan + 24 red seeds
a) Which is dominant, red or tan seeds?
b) Why did you answer as you did in a)?
c) What is the genotype of the F1 melons?
d) Look at the F2 results to decide whether the normal phenotypic ratio is within experimental
error of 3:1.

Explanation:

Lets Tan seed be TT

Red seed be tt

A cross between TT ×tt will produce 4 Tt

TT× tt

!

F1 Tt Tt Tt Tt

a. Tan seed is dominant with an allele TT. It effect dominate that of red seed indicating it is a dominant traits while red seed is a recessive traits.

A dominant trait is a traits that is expressed in the phenotype of an organism the F1 generation are all Tan seeds this shows that the trait is dominant.

The genotype of the F1 melon is Tt in a dominant form

The F2 result follows the mendelian principle where segregation occur leading to a phenotypic ratio of 3:1

72Tan seeds:24red seeds

Where the 72 tan seed has the highest ratio and 24 red seeds has the smaller ratio.

Tt ×Tt

!

F2 TT Tt Tt tt

Phenotypic ratio 3:1

your answer should be c) enjoy!