Model Paper 4 — BIOLOGY STD 12 Science — Question

Explain the inheritance of Sickle Cell anaemia.

Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Bovery with that of experimental results on pea plant presented by Mendel.

Given below is a schematic representation of a lac operon. Answer the following questions:

i. Identify i and p.
ii. Name the inducer for this operon.
iii. Explain the function of inducer for this operon.

Enlist the probable causes of infertility.

Suggest and describe a technique to obtain multiple copies of a gene of interest in vitro.

Why is the length of a food chain in an ecosystem generally limited to 3-4 trophic levels? Explain with an example.

In cattle, hornless (H) is dominant over horned (h) and black (B) is dominant over red (b). Consider that these two pairs of genes assort independently.

1. What proportion of the offspring from the cross, BbHh x bbhh, would be black and hornless?
2. From the cross Bbhh x Bbhh, how many will be:

1. Black and horned.
2. Red and horned.

Given below are the events that are observed in an artificial hybridisation programme. Selection of parents → Emasculation → Bagging → Collection of pollen from other male plant → Dusting of pollen on stigma — Rebagging.
While, planning for crop improvement involving dioecious plants, which of the above mentioned steps would not be relevant?

What is genetic code? How did genetic code came into existence ?