3) Children with ALD (pedigree at the left) have progressive brain damage. adrenal failure, and eventual...

3) Answer: c) Recessive

• Pdigree analysis: If the offspring are affected, but the parents are not affected (as they are heterozygous), then the condition is recessive.

4) Answer: X-linked.

• The X-linked traits are governed only by allele of X chromosome gene.
• X-linked inheritance affects mostly males. Males are affected in the pedigree, female passes the disease to males- sex linked. X-linked genes are transmitted from father to daughters and not to sons.
• ALD is Adrenoleukodystropy.
• It is prominent in males and is inherited as X-linked disorder.
• The condition affects the Adrenal gland and the nervous system.

5)

Representation:

Since the affected condition is recessive condition, representing as a, corresponding normal state as A.

Thus, genotypes may be represented as:

• Affected Male: Xa Y (hemizygous, recessive)
• Normal Male: XAY (hemizygous, dominant)
• Affected Female: XaXa (homozygous, recessive)
• Normal Female (carrier): XAXa (heterozygous, dominant)
• Since, the trait is passed from females to next to next generation male. The female of generation I and generation II are carriers.
• Genotype is heterozygous- XAXa