Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions

Rearrange the following in the correct sequence to accomplish an important biological reaction:

(a) In vitro synthesis of copies of DNA of interest

(b) Chemically synthesized oligonucleotides

(c) Enzyme DNA-polymerase

(d) Complementary region of DNA

(e) Genomic DNA template

(f) Nucleotides provided

(g) Primers

(h) Thermostable DNA-polymerase (from Thermus aquaticus)

(i) Denaturation of ds-DNA

State the role of DNA ligase in biotechnology.

Explain the work carried out by Cohen and Boyer that contributed immensely in biotechnology.

Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain.

Two heterozygous parents are crossed. If the two loci are linked, what would be the distribution of phenotypic features in the F₁ generation for a dihybrid cross?

Group the following as nitrogenous bases and nucleosides:

Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.

Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?

Give examples to prove that microbes release gases during metabolism.

In which food would you find lactic acid bacteria? Mention some of their useful applications.

Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.

Find out the role of microbes in the following:

Single cell protein (SCP)

What would be the molar concentration of human DNA in a human cell?

Distinguish between plasmid DNA and chromosomal DNA.

Distinguish between RNA and DNA.

How do ecologists estimate the total number of species present in the world?

What role does an individual organism play as per Darwin's theory of natural selection?

Mention the evolutionary significance of the Shrews

Mention the evolutionary significance of the Lobefins