Ecosystems — BIOLOGY STD 12 Science — Question

1. State the cause and symptoms of colour-blindness in humans.
2. Statistical data has shown that 8% of the human males are colour-blind whereas only 0.4% of females are colour-blind. Explain giving reasons how is it so.

Name and describe the steps involved in the technique widely used in forensics that serves as the basis of paternity testing in case of disputes.

A child suffering from thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby.

1. What is Thalassemia?
2. How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.
3. List the values your counselling can propagate in the families.

Show that Darwin's natural selection is based on theoretical factual observations, with an example for each.

Who revealed biochemical nature of the transforming principle? How was it done?

When does oogenesis start in humans? Name the three hormones and their source, linked with oogenesis. How do they influence the process of oogenesis? Explain.

Study the following flow chart. Name the hormones involved at each stage. Explain their functions.

Read the following and answer any four questions from (i) to (v) given below:
Crown gall is a neoplastic disease of most dicotyledonous plants and is caused by the soil bacterium Agrobacterium tumefaciens. A large extra chromosomal plasmid in these bacteria was found to be responsible for this disease. The plasmid is known as Ti plasmid. Bacteria free crown gall cells can be cultured in the absence of phytohormones. Ti plasmid is widely used in genetic engineering to deliver the desirable genes. The part of Ti plasmid transferred into plant cell DNA is called T-DNA. T-DNA with desired DNA segment is inserted into the chromosome of the host plant where it produces copies of itself.

1. Which of the following is the full full of T-DNA?

1. Transfer DNA.
2. Tumour inducing DNA.
3. Transgenic DNA.
4. None of these.

2. Ti plasmid cannot infect and develop crown gall in,

1. Tomato.
2. Maize.
3. Soybean.
4. sunflower.

3. While making transgenic plant, T-DNA is inserted into the host cell, it is then:

1. Integrated into the target host genome.
2. Lie independent of the host genome.
3. Rupture the host cell wall.
4. Produce oncogenic factors in the host.

4. Agrobacterium mediated gene transfer in plants:

1. Allows relatively large segment of DNA.
2. Transfer of DNA with defined ends and minimal rearrangement.
3. High quality and fertility in transgenic plants.
4. All of these.

5. Assertion: In Agrobacterium mediated gene transfer in plants, transgenic plants do not develop tumors.

Reason: In T-DNA tumor producing genes are deleted during the process of gene transfer.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

How does an electrostatic precipitator work?

Name any two chromosomal aberration associated disorders.