Question

Humans have a gene, "T" that is involved in muscle formation of the tongue. Individuals with the one allele can roll their tongues, while individuals with the other allele cannot. If both parents can roll their tongues, but their child cannot, what can be said about the mode of inheritance?A. Tongue-rolling is dominant.B. Tongue-rolling is recessive.C. The parents were both homozygous, while the child was heterozygous.D. Tongue-rolling is dominant, and both parents were heterozygous (Tt).E. Tongue-rolling is recessive, and both parents were heterozygous (Tt).

Answer 1

Answer:

Tongue-rolling is dominant, and both parents were heterozygous

Explanation:

Tongue rolling is a type of variation in human beings. When allelic genes are not identical as in Tt, the condition is referred to as heterozygous. An individual with such a genotypic condition is referred to as a heterozygote.

Both parents had a genotype of Tt and they could roll their tongues because T is dominant over the t gene.

              T     t

  T         TT   Tt

   t         Tt     tt

TT : Tt : tt

1 : 2 : 1

In a heterozygous parent Tt, the chance of producing T gamete from both parents is each 1/2 each. Similarly the chance of forming t gamete is 1/2. Therefore, the chance of gamete T and t fusing to get genotype Tt is 1/2*1/2=1/4.

The ratios of phenotypes are 3/4 will be able to roll the tongue and 1/4 will not be able to roll the tongue.

The mode of inheritance was monohybrid inheritance since one characteristic like tongue-rolling is controlled by a single pair of hereditary factors contributed by both parents.