Ecosystems and Energy Flow — BIOLOGY STD 12 Science — Question

Sympathetic nervous system.

Distinguish between: Active immunity and passive immunity.

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

Natality.

What is meant by traditional knowledge? What is its importance?

Describe in detail the steps involved in the replication of DNA.

Define transgenic animals. Explain in detail any four areas where they can be utilised.

Long Answer Questions
With the help of neat labelled diagram, describe the structure of chromosome.

Rose plants produce large, attractive bisexual flowers but they seldom produce fruits. On the other hand a tomato plant produces plenty of fruits though they have small flowers. Analyse the reasons for failure of fruit formation in rose.
Both these plants - rose and tomato - both selected by human beings for different characteristics, the rose for its flower and tomato for its fruit. Roses, being vegetatively propagated do not need to produce seeds.

Human female is not fertile after menopause whereas males can produce gametes at any age after puberty. Analyse the statement and schematically represent a comparison between gametogenesis in males and females.