1. In mutation A, the change in the codon GAG to GAA does not change the amino acid coded, i.e. both GAG and GAA code for amino acid glutamic acid; hence, there is no change in the haemoglobin structure.
2.In mutation B, the codon GAG is changed to GUG, where GUG codes for valine, while the original codon GAG codes for glutamic acid; hence, there is a change in the haemoglobin structure and it leads to sickle-cell anaemia.

Since dwarfness (recessive trait) has appeared in the progeny, the tall pea plant must be heterozygous for tallness, i.e. its genotype is Tt

1.The phenotypic ratio is 3 Tall : 1 dwarf.
2.Since tallness is dominant over dwarfness, the homozygotes (TT) as well as the heterozygotes (Tt) are tall.
3.The recessive trait is expressed only under homozygous condition (tt) and hence appears only in one-fourth of the progeny.

Test cross.In the cross ,if the individual is homozygous dominant, all terozygous, the progeny the individuals in the progeny will be dominant. If the individual is will show both he and recessive trait in the ratio of 1:1dominant.

By base pairing between the two strands that is adenine with thymine with two hydrogen bond and guanine with cytosine with 3 hydrogen bond.

The father genes are on a chromosome, the more frequently they will cross over. By comparison, the more frequently they will cross over.By comparison, genes that are close together on a chromosome, are less likely to be separated. The analysis of how often the traits appear together helps to establish linkage map, which shows the relative positions of genes on chromosomes.

It is an autosomal recessive trait that is not found in the parents, but has appeared irrespective of sex in the offspring. It this case, both the parents are heterozygous for the trait.

1.The gene for haemophilia is present in the X-chromosome.
2.The son receives the X-chromosome from his mother; so a carrier-mother passeson the disease to 50% of her sons.
3. When the mother is normal, the sons .have no chance of getting the disease, even if the father is haemophilic, because father passes on the Y-chromosome to his sons.

The other possible types of dominance are:
(i) Incomplete dominace.
e.g. Flower colour in snapdragon.
(ii) Codominance.
e.g. Blood group AB.

1. The characters are controlled by 'Factors' which are stably passed down without any change from the parents to the offspring, through the gametes.
2. The allels do not show any blending.

Since dwarfness (recessive trait) has appeared in the progeny, the tall pea plant must be heterozygous for tallness, i.e. its genotype is Tt

The phenotypic ratio is 3 Tall : 1 dwarf.
Since tallness is dominant over dwarfness, the homozygotes (TT) as well as the heterozygotes (Tt) are tall.
The recessive trait is expressed only under homozygous condition (tt) and hence appears only in one-fourth of the progeny.