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

Explain the role of ‘microinjection’ and ‘gene gun’ in biotechnology

Answer the following question.
β galactosidase enzyme is considered a better selectable marker. Justify the statement.

Answer the following question.
Expand ‘YAC’ and mention what it was used for.

Answer the following question.
Explain the significance of palindromic nucleotide sequence in the formation of recombinant DNA.

Answer the following question.
Write the use of restriction endonuclease in the formation of recombinant DNA.

What is the cell that receives a recombinant gene called?

Give a reason why :
Proteases are added during the isolation of DNA for genetic engineering.

Give a reason why :
Single cloning site is preferred in a vector.

How does the β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.

In a pathological lab, a series of steps were undertaken for finding the gene of interest. Describe the steps, or make a flow chart showing the process of amplification of this gene of interest.

The figure below shows the structure of a plasmid.

A foreign DNA was ligated at BamH1. The transformants were then grown in a medium containing antibiotics tetracycline and ampicillin.

Choose the correct observation for the growth of bacterial colonies from the given table.

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.

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.

Explain enzyme – replacement therapy to treat adenosine deaminase deficiency. Mention two disadvantages of this procedure.