Human Reproduction — BIOLOGY STD 12 Science — Question

Interspecific crosses are rare in nature and intergeneric crosses almost unknown. Why?

What are sacred groves and their role in biodiversity conservation?

Why medical termination of pregnancy is done? Is MTP legalised in India?

The cytological observations made in a number of insects led to the development of the concept of genetic/ chromosomal basis of sex-determination mechanism. Honey bee is an interesting example to study the mechanism of sex-determination. Study the schematic cross between the male and the female honey bees given below and answer the questions that follow:

1. Identify the cell divisions ‘A’ and ‘B’ that lead to gamete formation in female and male honey bees respectively.
2. Name the process ‘C’ that leads to the development of male honey bee (drone).

1. How may codons code for amino acids and how many are unable to do so?
2. Why are codes said to be.

1. Degenerate.
2. Unambiguous.

OR

1. How many codons code for amino acids and how many do not?
2. Explain the following giving one example of each.

1. Unambiguous and specific codon.
2. Degeneration codon.
3. Universal codon.
4. Initiator codon.

How BOD is related to water pollution?

Write the symptoms of haemophilia and sickle–cell anaemia in humans. Explain how the inheritance pattern of the two diseases differs from each other.

Mention the role of the following in E.coli cloning vector pBR 322.

1. Selectable marker.
2. ori.
3. rop.

1. Why does DNA replication occur in small replication forks and not in its entire length?
2. Why is DNA replication continuous and discontinuous in a replication fork?
3. Explain the importance of origin of replication' in a replication fork.

What is the association between the bumblebee and its favourite orchid Ophrys? How would extinction or change of one affect the other?