Respiration and Circulation — BIOLOGY STD 12 Science — Question

Is there any relationship between dedifferentiation and the higher degree of success achieved in plant tissue culture experiments?

1. A tRNA is charged with the amino acid methionine.

1. Name the process involved in the attachment.
2. Point out the mRNA codon and anticodon on RNA for this amino acid.

2. What is heterochromatin?

Since the origin of life on the earth, there were five episodes of mass extinction of species.

1. How is the 'Sixth Extinction', presently in progress, different from the previous episodes?
2. Who is mainly responsible for the 'Sixth Extinction'?
3. List any four points that can help to overcome this disaster.

1. Write the importance of measuring the size of a population in a habitat or an ecosystem.
2. Explain with the help of an example how the percentage cover is a more meaningful measure of population size than more numbers.

Differentiate between cleistogamous flower and chasmogamous flower.

What happens when there is insufficiency or deficiency of insulin in the body?

1. In a human genome, which one of the chromosomes has the most genes and which one has the fewest?
2. Scientists have identified about 1.4 million single nucleotide polymorphs in human genome. How is the information of their existence going to help the scientists?

Study the graph given below and answer the questions that follows.

1. Write the status of food and space in the curves A and B.
2. In the absence of predators, which one of the two curves would appropriately depict the prey population?
3. Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line.

How did the process of RNA interference help to control the nematode from infecting the roots of tobacco plants?
Or
How has RNAi technique helped to prevent the infestation of roots in tobacco plants by a nematode Meloidogyne incognita?

Why t-RNA is called as adapter molecule?