Human Health and Disease — BIOLOGY STD 12 Science — Question

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.

In a particular plant species, majority of the plants bear purple flowers. Very few plants bear white flowers. No intermediate colours are observed. If you are given a plant bearing purple flowers, how would you ascertain that it is a pure breed for that trait? Explain.

The generative cell of a two-celled pollen divides in the pollen tube but not in a three-celled pollen. Give reasons.

A tRNA is charged with the amino acid methionine:

1. At what site in the ribosome will the tRNA bind?
2. Give the anticodon of this tRNA.
3. What is the mRNA codon for methionine?
4. Name the enzyme responsible for this binding.

Where is sporopollenin present in plants? State its significance with reference to its chemical nature.

Calculate the length of the DNA of bacteriophage lambda that has 48502 base pairs.

How bacterial host cell is made competent to accept hydrophilic DNA, which allow DNA to pass through the cell membrane?

The total number of genes in humans is far less (< 25,000) than the previous estimate (upto 1,40,000 gene). Comment.

Draw a labelled diagram of the sectional view of a mature pollen grain of angiosperms. Explain the function of any two of its parts.

Write about application and future challanges of HGP