question_answer

In garden pea (Pisum sativum) a plant with red flowers was crossed with a plant with white flowers. Work out the possible genotypes and phenotypes of \[{{F}_{1}}\] and \[{{F}_{2}}\] generations. State any one of Mendel's law that could be derived from this cross.

OR

Mention any two autosomal genetic disorders with their symptoms.

 

Answer:

Mendel's law of dominance

The hybrid is heterozygous containing both alternative alleles (R and r) but only one trait, i.e., red colour appeared and white colour trait is suppressed in generation. This explains Mendel?s law of dominance.

OR

The autosomal genetic disorders are

(a) Down's Syndrome - It is caused due to an additional copy of chromosome number 21 or trisomy of chromosomes 21.

Its symptoms are:

(i) The diploid number of chromosomes in this case is 47. (45A+XX/XY)

(ii) Short statured, face rounded and flat, mouth open, tongue furrowed and saliva keeps dribbing.

(iii) Simian crease is prominent in the middle of the plam. Many loops on finger tips.

(iv) Mental and psychomotor development retarded. IQ is less than 25 (idiotic).

(b) Phenylketonuria - It is an inborn error of metabolism and is inherited as autosomal recessive trait.

The affected individual lacks an enzyme called phenylalanine hydroxylase that converts the ammo acid phenylalanine into tyrosine in liver. This phenylalanine is accumulated and converted into phenyl pyruvic acid and other derivatives in brain.

The symptoms are mental retardation, hypopigmentation of skin and eczema. The damage can be restricted if the child is fed on low-phenylalanine diet.