Dominance: is the condition when in a pair of dissimilar factors or alleles, one dominates the other that is one allele expresses itself in the presence or absence of the other allele. For example, the allele for tall trait T is dominant over the trait for dwarfness t.
Co-dominance: Co-dominance is the phenomenon in which both the alleles of a contrasting character are expressed in heterozygous condition. Both the alleles of a gene are equally dominant. ABO blood group system is an example of co-dominance.
Incomplete dominance: Incomplete dominance is a phenomenon in which one allele shows incomplete dominance over the other member of the allelic pair for a character. For example, a monohybrid cross between the plants having red flowers and white flowers in Antirrhinum species will result in all pink flower plants in F1generation.
The base sequence in one of the strands of DNA is TAGCATGAT.
(i) Give the base sequence of its complementary strand.
(ii) How are these base pairs held together in a DNA molecule?
(iii) Explain the base complementarity rules. Name the scientist who framed this rule.
(a) Sickle celled anaemia in humans is a result of point mutation. Explain.
(b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.
(a) Identify (A) and (B) illustrations in the following:
(b) Write the term given to (A) and (C) and why?
(c) Expand PCR. Mention its importance in biotechnology.
The diagram above is that of a typical biogas plant. Explain the seQ uence of events occurring in a biogas plant. Identify a, b and c.
How can crop varieties be made disease resistant to overcome food crisis in India? Explain.
Name one disease resistant variety in India of:
(a) Wheat to leaf and stripe rust
(b) Brassica to white rust
Write the source and the effect on the human body of the following drugs:
Name the type of interaction seen in each of the following examples:
(i) Ascaris worms living in the intestine of human
(ii) Wasp pollinating fig inflorescence
(iii) Clown fish living among the tentacles of sea-anemone
(iv) Mycorrhizae living on the roots of higher plants
(v) Orchid growing on a branch of a mango tree
(vi) Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland.
(a) Draw a labelled diagram of the human female reproductive system.
(b) Enumerate the events in the ovary of a human female during:
(i) Follicular phase
(ii) Luteal phase of menstrual cycle