Class 12th Biology 2014 Set3 Delhi Board Paper Solution

Mention the type of host cells suitable for the gene guns to introduce an alien DNA.

Name any two types of cells that act as 'cellular barriers' to provide innate immunity in humans.

How is repetitive/satellite DNA separated from bulk genomic DNA for various genetic experiments?

Write the name of the organism that is referred to as the 'Terror of Bengal'.

Name the greenhouse gases that contribute to global warming.

Identify 'a' and 'b' in the figure given below representing proportionate number of major vertebrate taxa.

Give an example of an organism that enters 'diapause' and why.

How is 'stratification' represented in a forest ecosystem?

(i) Name the scientist who suggested that the genetic code should be made of a combination of three nucleotides.

(ii) Explain the basis on which he arrived at this conclusion.

Explain with the help of a suitable example the naming of a restriction endonuclease.

Apart from being a part of the food chain, predators play other important roles. Mention any two such roles supported by examples.

Construct an age pyramid which reflects a stable growth status of human population.

Why does Bt toxin not kill the bacterium that produces it, but kill the insect that ingests it?

How does the gene 'I' control ABO blood groups in humans ? Write the effect the gene has on the structure of red blood cells.

OR

Write the types of sex-determination mechanisms the following crosses show. Give an example of each type.

(i) Female XX with Male XO

(ii) Female ZW with Male ZZ

Identify the following pairs as homologous of analogous organs:

(i) Sweet potato and potato

(ii) Eye of octopus and eye of mammals

(iii) Thorns of Bougainvillaea and tendrils of Cucurbits

(iv) Fore limbs of bat and whale

List the post-fertilisation events in angiosperms.

Study the graph given below and answer the questions that follow :

(i) Write the status of food and space in the curves (a) and (b).

(ii) In the absence of predators, which one of the two curves would appropriately depict the prey population?

(iii) Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line.

How did the process of RNA interference help to control the nematode from infecting the roots of tobacco plants?

What are methanogens? Name the animals in which methanogens occur and the role they play there.

(a) Name the tropical sugar cane variety grown in South India. How has it helped in improving the sugar cane quality grown in North India?

(b) Identify 'a', 'b' and 'c' in the following table:

Women are often blamed for producing female children. Consequently, they are ill-treated and ostracised. How will you address this issue scientifically if you were to conduct an awareness programme to highlight the values involved?

A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child. ​

OR

Mendel published his work on inheritance of characters in 1865, but it remained unrecognised till 1900. Give three reasons for the delay in accepting his work.

Name and explain the role of the inner and middle walls of the human uterus.

Explain any three advantages that seeds offer to angiosperms.

There are many animals that have become extinct in the wild but continue to be maintained in Zoological parks.

(i) What type of biodiversity conservation is observed in this case?

(ii) Explain any other two ways which help in this type of conservation.

(a) Name the technology that has helped scientists to propagate on a large scale the desired crops in a short duration. List the steps carried out to propagate the crops by the said technique.

(b) How are somatic hybrids obtained?

OR

(a) Cancer is one of the most dreaded diseases. Explain 'Contact inhibition' and 'Metastasis' with respect to the disease.

(b) Name the group of genes that have been identified in normal cells that could lead to cancer. How do these genes cause cancer?

(c) Name any two techniques that are useful in detecting cancers of internal organs.

(d) Why are cancer patients often given α-interferon as part of the treatment?

(a) Draw a labelled diagrammatic view of human male reproductive system.

(b) Differentiate between :

(i) Vas deferens and vasa efferentia

(ii) Spermatogenesis and spermiogenesis

OR

(a) Explain the phenomenon of double fertilisation. (b) Draw a labelled diagram of a typical anatropous ovule.

(a) Explain the process of DNA replication with the help of a schematic diagram.

(b) In which phase of the cell cycle does replication occur in Eukaryotes? What would happen if cell-division is not followed after DNA replication.

OR

(a) Explain Darwinian theory of evolution with the help of one suitable example. State the two key concept of the theory.

(b) Mention any three characteristics of Neanderthal man that lived in near east and central Asia.