Human Reproduction — BIOLOGY STD 12 Science — Question

Study the mRNA segment given below, which is complete and to be translated into a polypeptide chain and answer the following questions:

i. Write codons 'A' and 'B'.
ii. What do they code for?
iii. How is the peptide bond formed between two amino acids in the ribosome?

A new type of drug, PTC 124, enables translation to continue through the nonsense codon. Trials in mice homozygous for a CFTR allele containing the nonsense codon have found that animals treated with PTC 124 produce normal CFTR protein in their cells. The drug is taken orally and is readily taken up into cells all over the body.
Using your knowledge of the progress towards successful gene therapy for cystic fibrosis, suggest why PTC 124 could be simpler and more reliable treatment for this disease.

Name the host and the site where the following occur in the life-cycle of a malarial parasite:

1. Formation of gametocytes.
2. Fusion of gametocytes.

In a dihybrid cross white eyed, yellow bodied female Drosophila crossed with red eyed, brown bodied male Drosophila produced in F₂ generation, 1.3 per cent recombinants and 98.7 per cent progeny with parental type combinations. This observation of Morgan deviated from Mendelian F₂ phenotypic dihybrid ratio. Explain, giving reasons, Morgan’s observations.

Explain gene cloning.

Is it possible to achieve ‘zero population growth rate’? If yes, what kind of age pyramid is obtained?

Explain Connell's elegant field experiments.

What is amniocentesis? Why has the government imposed a statutory ban in spite of its importance in the medical field?

Explain divergent & convergent evolution with example.