Enhancement of Food Production — BIOLOGY STD 12 Science — Question

Observe the representation of genes involved in the lac operon given below.

1. Identify the region where the repressor protein will attach normally.
2. Under certain conditions repressor is unable to attach at this site. Explain.
3. If repressor fails to attach to the said site what products will be formed by z, y and a?
4. Analyse why this kind of regulation is called negative regulation.

A cross was carried out between a pea plant heterozygous for round and yellow seeds with a pea plant having wrinkled and green seeds.

1. Show the cross in a Punnett square.
2. Write the phenotype of the progeny of this cross.
3. What is this cross known as? State the purpose of conducting such a cross.

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

Explain the process of sewage water treatment before it can be discharged into natural bodies. Why is this treatment essential?

For selection of recombinants, insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chormogenic substrate. Give reasons.

Directional, Stabilizing and Disruptive selection.

Plasmids as cloning vectors.

Read the following and answer any four questions from (i) to (v) given below:
Transgenic animals can serve as factories that in some cases, may produce large amount of proteins more efficiently. Transgenic mice have been engineered to express human antibodies by introducing large segment of human DNA encoding human immunoglobulin genes. In transgenic large animals such as cow or sheep proteins of pharmaceutical value can be produced in large quantities in milk which is later purified. Transgenesis can be used to alter many phenotypic properties including growth rate, fat composition, milk production, hair texture, etc.

1. The production of transgenic animals includes

1. Identification and separation of desired gene.
2. Combining the desired gene with appropriate vector.
3. Introduction of vector in cells, tissues or embryos.
4. All of these.

2. In transgenic animals, i.e., cow and sheep proteins of pharmaceutical value are produced in large quantities in the

1. Blood.
2. Accumulated fat.
3. Mammary glands.
4. None of these.

3. Mouse is mostly preferred animal for studies on gene transfer because.

1. Short oestrous cycle.
2. Long gestation period.
3. Short generation time.
4. Production of one or two offspring per pregnancy.

1. Both (A) and (C)
2. Both (A) and (B)
3. Only D
4. Both (C) and (D).

4. Transgenic genes alter many phenotypic properties including:

1. Growth rate.
2. Fat composition.
3. Milk production.
4. All of these.

5. Assertion: Transgenic mice have been engineered to express human antibodies.

Reason: Large segment of human DNA encoding human immunoglobulin have been transferred to mice.

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.

Entomophily

Avinash went to his village during his summer vacations. One day, he decided to visit the nearby forest and asked his grandfather to accompany him. His grandfather told him about the recent cutting of forest and the new factory which had been established. Hearing this Avinash became curious and explained his grandfather about the ecosystem services.

1. What are the benefits of healthy forest ecosystem?
2. Explain the contribution of Robert Constanza in ecosystem services.
3. What factors account for cost of various ecosystem services?
4. What values are shown by Avinash?