Human Reproduction — BIOLOGY STD 12 Science — Question

A dihybrid heterozygous round, yellow seeded garden pea was crossed with a double recessive plant.

1. What type of cross is this?
2. Work out the genotype and phenotype of the progeny.
3. What principle of Mendel is illustrated through the result of this cross?

When someone buys packets of cigarettes, cannot miss the statutory warning that is present on the packing which warns against smoking and says how it is injurious to health. Yet, smoking is very prevalent in our society, both among young and old. Advise the adolescents about the importance of avoiding smoking. (Mention any six points.)

What is 'predation'? Explain with the help of suitable examples why is it required in a community with rich biodiversity.

Name three incurable sexually transmitted diseases and their causative organisms.

Identify the figure given alongside.

Differentiate between two different types of pyramids of biomass with the help of one example of each.

1. Mark the positive and negative terminals.
2. What is the charge carried by DNA molecule and how does it help in its separation?
3. How the separated DNA fragments are finally isolated?

What essential features must be present in a cloning vehicle/ cloning vector?

When Morgan conducted a dihybrid cross on Drosophila like Mendel did with pea plants, the F, ratios deviated significantly from that of Mendels F, ratio. Write the explanation Morgan and his group gave for the observations they obtained from their experiments.

Or

Morgan carried out several dihybrid crosses in Drosophila and found F, ratios deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of an example.

How do you distinguish between humification and mineralisation ?