CORRECTION TO ASSIGNMENT, QUESTION NUMBER TWO (2)

Question number two: A cross between different individuals with genotypes Tt and Tt for height was carried out.

i. Represent the percentage tall and the percentage short.

ii. What percentage is homozygously dominant, heterozygous, and homozygously recessive?

iii. What percentage is homozygous?

 

Answers:

When Tt and Tt is crossed, they will produce these possible genotypes in their first filial generation

TT

Tt

Tt

tt

The genotypes TT and Tt are phenotypically tall, while the genotype tt is phenotypical short. Since there are four genotypes, each genotype is 25% in 100%. Therefore, three genotypes are tall, being TT, Tt, and Tt.

i.e. 25*3 = 75

to sub-question i, the percentage phenotypically tall and short are 75 and 25, respectively.

Tall:short = 75:25

Sub-question ii. By homozygous dominant, it implies a gene in diploid organism, which has the two alleles being dominant (TT), the dominant here implies that a copy of an allele being present is enough to express the trait (T). Heterozygous recessive implies that the gene has one dominant and one recessive allele (Tt), while homozygous recessive implies that both alleles of the gene are recessive. By recessive, it implies that the phenotype is only expressed when the alleles are in pair (tt).

From

TT

Tt

Tt

tt

Percentage homozygous dominant is 25% i.e. only one set out of four sets is present.

Percentage heterozygous is 50% i.e. two sets out of four sets are present

Percentage homozygous recessive is 25% i.e. only one set out of four sets is present.

For sub-question iii. the percentage homozygous is 50%. because there is two homozygous genotypes (TT & tt) out of the four genotypes.