Plant Growth and Mineral Nutrition — BIOLOGY STD 12 Science — Question

In morphogenesis of plants cytokinin auxin ratio is important.

Explain the process of divergent evolution in detail. Also, write down the driving force behind it.

1. Explain the development of female gametophyte from a megaspore mother cell in an angiosperm.
2. Draw a leballed diagram of a fully-developed embryo sac.

OR

1. Describe the process of megasporogenesis in angiosperms, until 8-nucleate stage.
2. Draw the labelled structure of mature embryo sac.

Read the following and answer any four questions from (i) to (v) given below:
Gene therapy is the technique of genetic engineering to replace a faulty gene by a normal healthy functional gene. It is a way of treating genetic disease by introducing a piece of DNA into the cells of an affected individual. Liposomes can be used for gene therapy as they target the cells affected by a genetic disease.

1. A patient suffers from adenosine deaminase (ADA) deficiency, an autosomal recessive immune deficiency in which bone marrow lymphoblasts cannot replicate to generate immuno-competent lymphocytes. The treatment option that would cure the patient is:

1. Germ-line gene therapy to replace one ADA gene copy.
2. Germ-line gene therapy to replace both ADA gene copies.
3. Somatic cell gene therapy to replace both ADA gene copies in circulating lymphocytes.
4. Somatic cell gene therapy to replace one ADA gene copy in bone marrow lymphoblasts.

2. Which type of gene therapy is least effective in transferring DNA to the nucleus?

1. Adenoviruses.
2. DNA attached to a ligand.
3. Liposomes.
4. Retroviruses.

3. Liposomes can be used for gene therapy as they target the cells affected by a genetic disease. The diagram shows the structure of a liposome.

What feature of a cell surface membrane allows the liposome to target cells affected by a genetic disease?

1. Carrier molecules.
2. Phosphate groups.
3. Protein channels.
4. Receptor molecules.

4. Which of the following disorders would gene therapy be least effective?

1. Cystic fibrosis.
2. Huntington's disease.
3. Sickle cell anaemia.
4. Type II diabetes.

5. Following are some reasons explaining why gene therapy is not yet fully an effective treatment for genetic diseases.

1. Lack of knowledge of DNA sequences.
2. Lack of efficient and safe gene delivery system.
3. Cost of the technology.
4. Some diseases involve multiple genes.
5. Problems with appropriate gene regulation.

Select the correct option.

1. I, III and V only
2. II, IV and V only
3. Ill, IV and V only
4. I, III and IV only

Give schematic representation of nitrogen cycle and enlist important steps of this cycle.

Greenhouse effect.

A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.

1. Why in your opinion the female partner is often blamed for such situations in India? Mention any two values that you as a biology student can promote to check this social evil.
2. State any two reasons responsible for the cause of infertility.
3. Suggest a technique that can help the couple to have a child where the problem is with the male partner.

You are given a red flower–bearing pea plant and a red flower–bearing snapdragon plant. How would you find the genotypes of these two plants with respect to the colour of the flower? Explain with the help of crosses. Comment upon the pattern of inheritance seen in these two plants.

Describe the nature of inheritance of the ABO type of blood group in humans. In which ways does this inheritance differ from that of height of the plant in garden pea?

Distinguish between Parasitism and Mutualism