Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Read the following text carefully and answer the questions that follow:
A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes. The immune system of a person is suppressed. He was found positive for a pathogen in the diagnostic test ELISA.

i. Name the disease, the patient is suffering from. (1)
ii. Which pathogen is identified by ELISA test? (1)
iii. Which cells of the body are attacked by the pathogen? (2)
OR
Suggest preventive measures of the infection. (2)

What is oogenesis? Give a brief account of oogenesis.###Define or Characterise: (i) Primary oocyte. (ii) Primary follicle. (iii) Secondary follicle. (iv) Tertiary follicle. (v) Antrum. (vi) Secondary oocyte. (vii) Graafian follicle.

Read the following and answer any four questions from (i) to (v) given below:
Rohan, a 13 year old school student, has been diagnosed with AIDS. He often complains of fever, nausea, headache and lethargy. Doctor advised some drugs to prolong his life.

1. What could be the most likely mode of transmission of disease to Rohan?

1. Artificial insemination.
2. Sexual intercourse with infected partner.
3. Sexual intercourse with infected partner.
4. Use of contaminated blade.

2. Name the drug prescribed for treatment of this disease.

1. Zidovudine.
2. Taxol.
3. Vinblastine.
4. Both (a) and (c).

3. Assertion: AIDS is an incurable STD.

Reason: AIDS virus attacks helper T-lymphocytes.

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.

4. AIDS cannot be diagnosed by:

1. ELISA.
2. PCR.
3. Western blotting.
4. VDRL.

5. AIDS can be transmitted by:

1. Sharing towels.
2. Kissing.
3. Sharing contaminated needles.
4. All of these.

1. What are the three options that can be thought of, to increase food production?
2. Mention the reasons for the success of Green Revolution in increasing food production.
3. Why do we still search for other alternatives to increase food production?

Read the following text carefully and answer the questions that follow:
Gene regulation is the mechanism of switching off and switching on of the genes depending upon the requirement of cells and the state of development. Gene regulation is of two types: negative and positive. In negative gene regulation, the genes continue expressing their effect till their activity is suppressed. Positive gene regulation is the one in which the genes remain non-expressed unless and until they are induced to do it. Operon model is a co-ordinated group of genes such as structural gene, operator gene, promoter gene, regulator gene which function together and regulate a metabolic pathway as a unit, e.g., lac operon, trp operon, ara operon, etc.

i. Regulation of gene expression occurs at which the level? (1)
ii. What is complementary to an mRNA molecule transcribed from the lac operon contains nucleotide sequences? (1)
iii. Describes the control of transcription of the genes involved in the breakdown of lactose in Escherichia coli?
(2)
OR
What is the function of catabolic activator protein in lac operon? (2)

Given below is the pattern of temperature in a person suffering from a non-viral disease transmitted by mosquitoes. Study the graph and answer the questions that follow:

A. Explain the factor(s) responsible for this pattern of temperature.
B. How does this pathogen multiply in the human body?
C. How is this infection transmitted to humans?
OR
D. Which stages of the life cycle of this pathogen are completed in the mosquito's gut?

Explain Species-Area relationships graph.

What is sewage? Describe secondary treatment (biological treatment) in Sewage Treatment plant.

Read the following and answer any four questions from (i) to (v) given below:
A typical angiospermic ovule is a small structure attached to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is formed. Mature ovules are classified on the basis of funiculus. It can be orthotropous, anadromous, hernitropous, campylotropous, etc.

1. The body of the ovule consists of a mass of parenchymatous cells called:

1. Integuments.
2. Nucellus.
3. Hilum.
4. Funiculus.

2. Refer to the given figure and select the correct statement regarding it.

1. This type of ovule is found in cactus.
2. The micropyle comes to lie close to the funiculus due to unilateral growth of ovule.
3. It is most common type of ovule found in the members of Chenopodiaceae.
4. It is half inverted ovule.

3. Identify the parts labelled as A, B, C and D in the given figure and select the correct option.

S. No	A	B	C	D
(a)	Chalaza	Female gametophyte	Embryo sac	Micropyle
(b)	Chalaza	NuceIIus	Embryo sac	Micropyle
(c)	Micropyle	Egg	Embryo sac	Chalaza
(d)	Micropyle	Nucellus	Embryo sac	Chalaza

4. Mature ovules are classified on the basis of funiculus. If micropyle lie close to the funiculus, the ovule is termed as:

1. Orthotropous.
2. Anatropous.
3. Hemitropous.
4. Campylotropous.

5. In Asphodel us, ovule is:

1. Unitegmic.
2. Tritegmic.
3. Bitegmic.
4. Ategmic.