Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

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.

Different animals respond to changes in their surroundings in different ways. Taking one example each, explain "some animals undergo aestivation while some others hibernation". How do fungi respond to adverse climatic conditions?

How many sperms will be produced from 50 primary spermatocytes?

A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air, identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions.

How can a bioreactor be made to function at optimal state in order to obtain a desired foreign gene product? Explain.

Mention the functions of trophoblast in human embryo.

Give information about pills & Explain How it is useful as a contraceptive ?

With respect to Messelson and Stahl’s Experiment, answer the following questions:

1. Identify the method used to distinguish between heavy and light isotopes of nitrogen.
2. With the help of diagrams, compare the results for the DNA isolated after 20 minutes of experiment with the DNA which was isolated after 40 minutes.

What is a test cross? How can it decipher the heterozygosity of a plant?

A team of students are preparing to participate in the interschool sports meet. During a practice session, you find some vials with labels of certain cannabinoids.

1. Will you report to the authorities? Why?
2. Name a plant from which such chemicals are obtained.
3. Write the effect of these chemicals on human body.