(a) State the cause and symptoms of Down's syndrome.  Name and explain the event responsible for causing this syndrome.
(b) Haemophilia and Thalassemia are both examples of Mendelian disorders, but show differences in their inheritance pattern.  Explain how.

5

(a)

Differentiate between the following:
(a) Polgenic inheritance and Pleiotropy
(b) Dominance, Codominance and Incomplete dominance

5

(a)

(a) Explain the genetic basis of ABO blood groups in human population.
(b) How do ABO blood groups explain the phenomena of dominace and codominance?

5

(a)

Describe the mechanism of pattern of inheritance of ABO blood groups in humans.

5

(a)

Haemophilia and sickle-cell anaemia are blood related Mendelian disorders. Yet, they differ in their pattern of inheritance. Explain the difference.

5

(a)

A particular garden pea plant produces only violet flowers.  It may or may not be homozygous dominant for the trait.  How would you ensure the genotype.  Explain with crosses.

5

(a)

State the law that Mendel proposed on the basis of such a cross.

5

(a)

What exactly is dominance?  Why are some alleles dominant and some recessive?

5

(a)

Explain Monohybrid cross.

5

(a)