Biotechnology and its Applications — BIOLOGY STD 12 Science — Question

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:

Over population causes number of family problems. Strategies like birth control methods help to control population explosion. Natural methods of birth control do not involve medications or devices to prevent pregnancy, but rather rely on behavioural practices and/ or making observations about menstrual cycle.

1. Which method helps in contraception by temporary absence of sex?

1. Coitus interruptus.
2. Withdrawal method.
3. Rhythm method.
4. Lactational amenorrhea method.

2. Assertion: The effectiveness of coitus interruptus method is limited.

Reason: Some sperms may pass into vagina before ejaculation.

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.

3. Why is lactational amenorrhea effective for about 4-5 months after parturition?

1. Ovulation occurs on about the 14^th day of menstruation.
2. Ovulation does not occur during intense lactation.
3. This method inhibits mobility of sperms.
4. Both (b) and (c).

4. Which fact is not the basis of periodic absence method of birth control?

1. Ovum remains alive for about 1-2 days.
2. Ovulation occurs on about 14^th day of menstruation.
3. Sperms survive for about 3 days.
4. Alteration in uterine endometrium.

5. On which days of menstrual cycle should coitus be avoided to prevent fertilisation?

1. 10-17
2. 6-13
3. 1-5
4. 15-28

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.

Define ecological pyramids and describe with examples, pyramids of number and biomass.

Read the following text carefully and answer the questions that follow:
When a microorganism invades a host, a definite sequence of events usually occur leading to infection and disease, causing suffering to the host. This process is called pathogenesis. Once a microorganism overcomes the defense system of the host, development of the disease follows a certain sequence of events as shown in the graph. Study the graph given below for the sequence of events leading to appearance of a disease and answer the questions that follow:

i. In which period, according to the graph there are maximum chances of a person transmitting a disease/infection and why? (1)
ii. Study the graph and write what is an incubation period. Name a sexually transmitted disease that can be easily transmitted during this period. Name the specific type of lymphocytes that are attacked by the pathogen of this disease. (1)
iii. Draw a schematic labelled diagram of an antibody. (2)
OR
In which period, the number of immune cells forming antibodies will be the highest in a person suffering from pneumonia?
Name the immune cells that produce antibodies. (2)

Explain pBR322 with its cloning sites, enzymes with well labeled diagram.###Explain: cloning sites. (Diagram is not necessary)

Read the following text carefully and answer the questions that follow:
When a microorganism invades a host, a definite sequence of events usually occur leading to infection and disease, causing suffering to the host. This process is called pathogenesis. Once a microorganism overcomes the defense system of the host, development of the disease follows a certain sequence of events as shown in the graph. Study the graph given below for the sequence of events leading to appearance of a disease and answer the questions that follow:

i. In which period, according to the graph there are maximum chances of a person transmitting a disease/infection and why? (1)
ii. Study the graph and write what is an incubation period. Name a sexually transmitted disease that can be easily transmitted during this period. Name the specific type of lymphocytes that are attacked by the pathogen of this disease. (1)
iii. Draw a schematic labelled diagram of an antibody. (2)
OR
In which period, the number of immune cells forming antibodies will be the highest in a person suffering from pneumonia?
Name the immune cells that produce antibodies. (2)

Explain any two X-linked recessive disorder?

Explain in situ approach for conservation of biodiversity.

Assuming that within a population of beetles where Hardy Weinberg conditions are met, the colour black (B) is dominant over the colour red (b). 40% of all beetles are red (bb).
Given this information, answer the questions below:
A. What is the frequency of red beetles?
B. Calculate is the percentage of beetles in the population that are heterozygous.
C. What is the frequency of homozygous dominant individuals?
OR
D. Assuming that Hardy Wienberg conditions are met in the beetle population consisting of 1500 beetles. How many beetles would you expect to be black and red in colour respectively?