Science (English Medium) Class 12 - CBSE Question Bank Solutions for Biology

State the importance of elution in this process.

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.

Given below are the list of the commercially important products and their source organisms. Select the option that gives the correct matches. 

Name and explain a surgical contraceptive method that can be adopted by the male partner of a couple.

'EcoRI' has played a very significant role in rDNA technology.

1. Explain the convention for naming EcoRI.
2. Write the recognition site and the cleavage sites of this restriction endonuclease.

What are the protruding and hanging stretches of DNA produced by these restriction enzymes called? Describe their role in the formation of rDNA.

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

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

Given below are the structural details of a human mammary gland:

1. The glandular tissue in the breast has 15-20 clusters. of cells called alveoli.
2. The milk is stored in the lumen of the alveoli.
3. The alveoli join to form the mammary ducts.
4. Mammary ampulla is connected to lactiferous ducts.

Choose the option that gives the correct detail of the human mammary gland.

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

Given below are certain situations. Analyse the situation and suggest the name of suitable contraceptive device along with mode of action.

Name the selectable markers in the cloning vector pBR322. Mention the role they play.

Explain the different steps involved during primary treatment phase of sewage.

Explain the process of secondary treatment given to the primary effluent up to the point it shows significant change in the level of biological oxygen demand (BOD) it.

State how has Agrobacterium tumifaciens been made a useful cloning vector to transfer DNA to plant cells.

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

What is primary productivity?

How is 'oogenesis' markedly different from 'spermatogenesis' with respect to the growth till puberty in the humans?

Draw a sectional view of human ovary and label the different follicular stages, ovum and Corpus luteum.

Write the equation that helps in deriving the net primary productivity of an ecosystem.