Board Paper of Class 12-Science 2013 Biology (SET 3) - Solutions

Why is the enzyme cellulase needed for isolating genetic material from plant cells and not form the animal cells?

Write the importance of MOET.

An anther with malfunctioning tapetum often fails to produce viable male gametophytes. Give any one reason.

Why sharing of injection needles between two individuals is not recommended?

Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule.

“Sweet potato tubers and potato tubers are the result of convergent evolution.” Justify the statement. (1)

Write the equation that helps in deriving the net primary productivity of an ecosystem.

Name the type biodiversity represented by the following:

(a) 50,000 different strains of rice in India.

(b) Estuaries and alpine meadows in India

Explain why very small animals are rarely found in polar region.

Why the pyramid of energy is always upright? Explain.

Expand the following and mention one application of each:

(i) PCR

(ii) ELISA

OR

(a) Mention the difference in the mode of action of exonuclease and endonuclease.

(b) How does restriction endonuclease function? 

Name any two sources of e-Wastes and write two different ways of their disposal.

Explain the steps that ensure cross pollination in an autogamous flower. (2)

When and where do chorionic villi appear in humans? State their function.

In a cross between two tall pea plants some of the offsprings produced were dwarf. Show with the help of Punett square how this is possible.

A student on a school picnic to park on a windy day started sneezing and having difficulty in breathing in reaching the park. The teacher enquired whether the student was allergic to something.

(a) What is an allergy?

(b) Write the two unique characteristics of the system involved in the response observed in the student. (2)

Why and how bacteria can be made ‘competent’? (2)

(a) Name the deficiency for which first clinical gene therapy was given.

(b) Mention the cause of and one cure for this deficiency. (2)

(a) Why is human ABO blood group gene considered a good example of multiple alleles?

(b) Work out a cross up to F₁ generation only, between a mother with blood group A (Homozygous) and the father with blood group B (Homozygous). Explain the pattern of inheritance exhibited. (3)

Describe the structure of RNA polynucleotide chain having four different types of nucleotides.

(a) Differentiate between inbreeding and outbreeding.

(b) Explain inbreeding depression and how it can be overcome.

(c) Mention two advantages of inbreeding programme in cattle. (3)

(a) Why are the fruit juices bought from market clearer as compared to those made at home?

(b) Name the bioactive molecules produced by Trichoderma polysporum and Monascus purpureus.

Draw the following diagrams related to human reproduction and label them.

(a) The zygote after the first cleavage division

(b) Morula stage

(c) Blastocyst stage (sectional view) (3)

With the help of any two suitable examples explain the effect of anthropogenic actions on organic evolution. 

How have human activities caused desertification? Explain.

OR

How does algal bloom destroy the quality of a fresh water body? Explain. 

Explain mutualism with the help of any two examples. How is it different from commensalism? (3)

(a) Why a transgenic animals so called?

(b) Explain the role of transgenic animals in (i) Vaccine safety and (ii) Biological products with the help of an example each. (3)

A child suffering from Thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby.

(a) What is Thalassemia?

(b) How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.

(c) List the values your counselling can propagate in the families.

Draw a diagram of a mature embryo sac of an angiosperm and label the following parts in it.

(i) Filiform apparatus

(ii) Synergids

(iii) Central cell

(iv) Egg cell

(v) Polar nuclei

(vi) Antopodals

(b) Write the fate of egg cell and polar nuclei after fertilization.

OR

(a) Describe the events of Oogenesis with the help of schematic representation.

(b) Write two differences between Oogensis and spermatogenesis.

Describe the asexual and sexual phases of life cycle of Plasmodium that causes malaria in humans. (5)

OR

(a) What is plant breeding? List the two steps the classical plant breeding involves.

(b) How has the mutation breeding helped in improving crop varieties? Give one example where this technique has helped.

(c) How has the breeding programme helped in improving the public nutritional health? State two examples in support of your answer.