Control and Co-ordination — BIOLOGY STD 12 Science — Question

Distinguish between: Primary sex organs and Secondary sex organs.

Read the following and answer any four questions front (i) to (v) given below:
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 generegulation 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.

1. Regulation of gene expression occurs at the level of.

1. Transcription
2. Processing/splicing
3. Translation
4. All of these.

2. Inducible operon system usually occurs in A pathways. Nutrient molecules serve as B to stimulate production of the enzymes necessary for their breakdown. Genes for inducible operon are usually switched C and the repressor is synthesised in an D form.

S.no	A	B	C	D
(a)	anabolic	corepressor	on	inactive
(b)	anabolic	inducer	off	active
(c)	catabolic	inducer	off	active
(d)	catabolic	corepressor	on	inactive

3. An mRNA molecule transcribed from the lac operon contains nucleotide sequences complementary to.

1. Structural genes coding for the enzymes.
2. the operator region
3. the promotor region
4. the repressor gene.

4. Which statement correctly describes the control of transcription of the genes involved in the breakdown of lactose in Estherichia coli?

1. A repressor protein binds to the operator and the genes are switched on.
2. A repressor protein binds to the operator and the genes are switched off.
3. A transcription factor binds to the promoter and the genes are switched on.
4. A transcription factor binds to the promoter and the genes are switched off.

5. Function of catabolic activator protein in lac operon is.

1. To form mRNA
2. Help to bind RNA polymerase
3. Code for repressor
4. To activates lac gene when glucose is absent.

Distinguish between : Eosinophils and Basophils.

Read the following and answer any four questions from (i) to (v) given below:
Age sex structure of a population can be depicted in the form of a pyramid by plotting the percentage of population of each sex in each age class. Two age sex pyramids are as follows.

1. Which of the following is correct regarding pyramid B?

1. It represents stable population.
2. It represents expanding population.
3. It represents declining population.
4. Both (a) and (b).

2. Total number of individuals of a species per unit area per unit time is called.

1. Population size.
2. Population density.
3. Demography.
4. Population dynamics.

3. Which of the following is correct regarding age sex pyramid A and B?

1. A represents the age sex pyramid of developed country.
2. B represents the age sex pyramid of developing country.
3. A represents rapidly growing population.
4. Both (a) and (b).

4. A population with a large proportion of older individuals than younger ones will likely to:

1. Grow larger first and then decline.
2. Continue to grow indefinitely.
3. Decline.
4. None of these.

5. Assertion: Bell shaped age pyramid represents a stable population.

Reason: ln a stable population, proportion of individuals in reproductive age group is higher than the individuals in pre reproductive age group.

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.

Read the following and answer any four questions from (i) to (v) given below:
Aditya went to his hometown located in countryside along with his parents during his summer vacations. His grand parents' house is surrounded by farmland from all sides. Lots of crops were growing nearby and Aditya was very excited to visit the crop fields. He seeked permission from his mother to play in farmland along with his friends and then went to play in the fields. On returning back he had running nose, watering eyes and continuous sneezing which was very frequent. TI1e symptoms worsened with time. Based on the above information, answer the following questions.

1. What could be the possible reason for Aditya's condition?

1. Allergy
2. Infection
3. Malnutrition
4. Genetic disorder

2. How can allergy be diagnosed in a person?

1. Presence of large amount of IgE antibodies in the blood.
2. Presence of large number of bacteria in the blood.
3. Presence of bilirubin and bilirubin pigments in the stool.
4. Presence of sickle shaped RBCs in the blood

3. The symptoms which Aditya developed on account of being allergic are consequence of?

1. Inflammation of membrane lining the nose and conjunctiva
2. Swelling up of tissue surrounding bronchioles of lungs
3. Dilation of all arteries so that large amount of fluid passes from blood to tissues.
4. All of these.

4. Name the type of allergy that Aditya developed.

1. Asthma
2. Anaphylaxis
3. Hay fever
4. Urticaria

5. Assertion : Hay fever is the form of allergy due to pollens of grasses and other plants.

Reason : Hay fever symptoms are due to release of histamines and often respond well to treatment with antihistamines.

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.