Question

What is autosomal inheritance? Explain different disorders due to autosomal inheritance.

Answer 1

Definition: 
Transmission of body characters other than the sex-linked traits from parents to their offsprings through autosomes is called autosomal inheritance.

1. Widow’s Peak
   a. A prominent ‘V’ shaped hairline on the forehead is described as a widow’s peak. It is determined by an autosomal dominant gene.
   b. Widow’s peak occurs in homozygous dominant (WW) and also heterozygous (Ww) individuals.
   c. Individuals with homozygous recessive (WW) genotype have a straight hairline (no widow’s peak).
   d. Both males and females have an equal chance of inheritance.
2. Phenylketonuria
   a. Phenylketonuria is an inborn metabolic disorder caused due to deficiency of phenylalanine hydroxylase enzyme.
   b. Phenylketonuria is caused due to recessive autosomal genes.
   c. When recessive genes are present in homozygous conditions, phenylalanine hydroxylase enzyme is not produced.
   This enzyme is essential for
   d. conversion of amino acid phenylalanine into tyrosine.
   e. Due to the absence of this enzyme, phenylalanine is not converted into tyrosine.
   f. Hence, phenylalanine and its derivatives are accumulated in blood and cerebrospinal fluid (CSF).
   g. It affects the development of the brain and causes mental retardation.
   h. Excess phenylalanine is excreted in the urine, hence this disease is called phenylketonuria.