Evolution — BIOLOGY STD 12 Science — Question

Answer the following questions:
How did Morgan show the deviation in inheritance pattern in Drosophila with respect to this law?

Describe the molecular structure of DNA by making a labelled diagram.

What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance?

What is cancer? How is a cancer cell different from normal cell? How do normal cells attain cancerous nature?

Explain the development of a secondary oocyte (ovum) in a human female from the embryonic stage upto its ovulation. Name the hormones involved in this process.OR
When does oogenesis start in humans? Name the three hormones and their sources, linked with oogenesis. How do they influence the process of oogenesis? Explain.

Describe the functions of the following:
Seminiferous tubules.

1.  

1. Name the biogeochemical (nutrient) cycle shown below:
2. Name an activity of the living organisms not depicted in the cycle by which this nutrient is returned to the atmosphere.

2. How would the flow of nutrient in the cycle be affected due to large scale deforestation? Explain giving reasons.
3. Describe the effect of an increased level of this nutrient in the atmosphere on our environment.

1. One of the sperms is observed to penetrate 'a' of the ovum, as shown in the above diagram. Name 'a'.
2. How is the sperm able to do so?
3. Where exactly in the fallopian tube does this occur?
4. Explain the events thereafter up to morula stage.

A pea plant bearing axial flowers is crossed with a pea plant bearing terminal flowers. The cross is carried out to find the genotype of the pea plant bearing axial flowers. Work out the cross to show the conclusions you arrive at.

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.