Human Health and Diseases — BIOLOGY STD 12 Science — Question

Name the common function that cotyledons and nucellus perform.

Bring out the differences between secondary and tertiary follicles.

A3' ............ 5'B
C5’ ........... 3'D.
AB and CD represent two strands of a DNA molecule. When this molecule undergoes replication, forming a replication fork between A and C in the above.

1. Name the templete strand for replication.
2. Using which strand as the templete, will there be continuous synthesis of a complementary DNA strand
3. Complementary to which strand will okazaki segments get synthesised, discontinuous synthesis occurs.
4. What are templete strands and Okazaki pieces?
5. In which direction is a new strand synthesised?

Recall the experiments done by Frederick Griffith, Avery, MacLeod and McCarty, where DNA was speculated to be the genetic material. If RNA, instead of DNA was the genetic material, would the heat killed strain of Pneumococcus have transformed the R-strain into virulent strain? Explain.

Mention the major cause of air pollution in metro cities. Write any three ways by which it can be reduced.

Which chromosome carries the mutated gene causing β–thalassemia? What are the problems caused by the mutation?

What is cryopreservation? Give it's one use.

Discuss the role the enzyme DNA ligase plays during DNA replication.

Which are the three cells found in a pollen grain when it is shed at the three-celled stage?

Name a few enzymes involved in DNA replication other than DNA polymerase and ligase. Name the key functions for each of them.