Class 12th Biology 2015 Set3 Delhi Board Paper Solution

Name the transcriptionally active region of chromatin in a nucleus.

A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms for experiments with shorter life cycle. Provide a reason.

What is Biopiracy ?

State a reason for the increased population of dark coloured moths coinciding with the loss of lichens (on tree barks) during industrialization period in England.

Indiscrimate diagnostic practices using X-rays etc., should be avoided. Give one reason.

Differentiate between 'ZZ' and 'XY' type of sex-determination mechanisms.

An infertile couple is advised to adopt test-tube baby programme. Describe two principle procedures adopted for such technologies.

Many fresh water animals can not survive in marine environment. Explain.

OR

How are productivity, gross productivity, net primary productivity and secondary productivity interrelated ?

Enumerate four objectives for improving the nutritional quality of different crops for the health benefits of the human population by the process of "Biofortification".

Mention a product of human welfare obtained with the help of each one of the following microbes :

(a) LAB

(b) Saccharomyces cerevisiae

(c) Propionibacterium shermanii

(d) Aspergillus niger

Describe the process of Parturition in humans.

Describe the development of endosperm after double fertilisation in an angiosperm. Why does endosperm development preceeds that of zygote ?

Explain the interpretation of Charles Darwin when he observed a variety of smallblack birds on Galapagos Islands.

A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible.

(a) A DNA segment has a total of 2,000 nucleotides, out of which 520 are adenine containing nucleotides. How many purine bases this DNA segment possesses ?

(b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.

Recombination DNA technology is of great importance in the field of medicine. With the help of a flow chart, show how this technology has been used in preparing genetically engineered human insulins.

Draw a labelled sketch of sparged-stirred-tank bioreactor. Write its application.

Following the collision of two trains a large number of passengers are killed. A majority of them are beyond recognition. Authorities want to hand over the dead to their relatives. Name a modern scientific method and write the procedure that would help in the identification of kinship.

A team of students are preparing to participate in the interschool sports meet. During a practice session you find some vials with labels of certain cannabinoids.

(a) Will you report to the authorities? Why?

(b) Name of a plant from which such chemicals are obtained.

(c) Write the effect of these chemicals on human body.

Many plant and animal species are on the verge of their extinction because of loss of forest land by indiscriminate use by the humans. As a biology student what method would you suggest along with its advantages that can protect such threatened species from getting extinct ?

OR

"Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body." Explain.

Enlist the steps involved in inbreeding of cattle. Suggest two disadvantages of this practice.

Choose any three microbes, from the following which are suited for organic farming which is in great demand these days for various reasons. Mention one application of each one chosen.

Mycorrhiza; Monascus; Anabaena; Rhizobium; Methanobacterium; Trichoderma.

Since October 02, 2014 "Swachh Bharat Abhiyan" has been launched in our country.

(a) Write your views on this initiative giving justification.

(b) As a biologist name two problems that you may face while implementing the programme in your locality.

(c) Suggest two remedial methods to overcome these problems.

Explain the genetic basis of blood grouping in human population.

OR

How did Hershey and Chase established that DNA is transferred from virus to bacteria?

"Analysis of age-pyramids for human population can provide important inputs for long-term planning strategies." Explain.

OR

Describe the advantages for keeping the ecosystems healthy.

A flower of tomato plant following the process of sexual reproduction produces 200 viable seeds.

Answer the following questions giving reasons :

(a) What would have been the minimum number of ovules present in pre-pollinated pistil ?

(b) How many microscope mother cells would minimally be required to produce requisite number of pollen grains ?

(c) How many pollen grains must have minimally pollinated the carple ?

(d) How many male gametes would have used to produce these 200 viable seeds ?

(e) How many megaspore mother cells were required in this process ?

OR

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.