Science (English Medium) इयत्ता १२ - CBSE Important Questions for Biology

CTTAAG
GAATTC

1. What are such sequences called? Name the enzyme used that recognizes such nucleotide sequences.
2. What is their significance in biotechnology?

Carefully observe the given picture. A mixture of DNA with fragments ranging from 200 base pairs to 2500 base pairs was electrophoresed on agarose gel with the following arrangement.

(a) What result will be obtained on staining with ethidium bromide? Explain with reason.

(b) The above setup was modified and a band with 250 base pairs was obtained at X.

What change(s) were made to the previous design to obtain a band at X? Why did the band appear at position X?

(a) List two advantages of using bacteria for such biotechnological studies?

(b) For amplification of the gene of interest PCR was carried out. The PCR was run with the help of polymerase which was functional only at a very low temperature. How will this impact the efficiency of the PCR? Justify.

(c) If such bacteria are sprayed on water bodies with oil spills, how will this have a positive or negative effect on the environment? Discuss.

Non viral and non vector methods are sometimes used to transfer genes or alien DNA into a plant cell. Explain one such method used in genetic engineering.

Given below is the restriction site of a restriction endonuclease Pst-I and the cleavage sites on a DNA molecule.

\[\ce{5' C - T - G - C - A \overset{\downarrow}{-}{G 3'}}\]

\[\ce{3' G\underset{\uparrow}{-} A - C - G - T - C 5'}\]

Choose the option that gives the correct resultant fragments by the action of the enzyme Pst-I.

State the principle involved in separation of DNA fragments using gel electrophoresis.

How are DNA fragments visualised once they are separated by gel electrophoresis?

Identify the activity of endonuclease and exonuclease in the given image.

The structure below shows pUC18, which is similar to pBR322 in its function. However, they differ in some of their restriction sites and the number of ori. The ori number for pBR322 is approximately 20.

1. How are puc18 and pBR322 used in biotechnological studies?
   OR
   What will be the impact if the ori in the above structure gets damaged?
2. The lac z gene has many recognition sites. Study the segment of DNA given below and answer the questions.
   5’... ATC GTA AAG CTT CAT…3’
   3’... TAG CAT TTC GAA GTA…5’
   i) Applying your knowledge of palindrome sequences identify and mark the possible region where the restriction enzyme X will act.
   ii) Restriction enzyme Y was used to extract a gene of interest from a plant. This gene needs to be inserted in the given DNA segment which has been treated with restriction enzyme X. Will there be a successful recombination? Explain with a reason.
3. Which one of the two (pUC18 and pBR322) would you prefer for biotechnological studies? Justify.

Why a transgenic animals so called?

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

Why has the Indian Government set up the organisation named GEAC ? Give any two reasons.

"Artificial insemination helps overcome several problems of normal mating in cattle". Do you agree? Support your answer with any three reasons.

A patient admitted in ICU was diagnosed to have suffered from myocardial infarction. The condition of coronary artery is depicted in the image below.

Name two bioactive agents and their mode of action that can improve this condition.

(a) Name the two growth models that represent population growth and draw the respective growth curves they represent.

(b) State the basics for the difference in the shape of these curves

(c) Which one of the curves represents the human population growth at present? Do you think such a curve is sustainable? Give reason in support of your answer.

Explain mutualism with the help of any two examples.

Write what do phytophagous insects feed on.

Why do clown fish and sea anemone pair up? What is this relationship called?

How do mycorrhizae help the plants to grow better?  

How is mutualism different from commensalism?