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

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

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

Eli Lilly's contribution for diabetic patients through r-DNA technology has been overwhelmingly accepted. Explain how?

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.

• Assertion: PCR is a powerful technique to identify genetic disorders.
• Reason: PCR can detect mutations in low amounts of DNA.

The graph given below indicates the administration of the first (L) and second dose (M) of a vaccine. The corresponding response of the body is indicated by X, and Y. Interpret the graph and explain the reason for such a response shown by the body.

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

Illustrate using any one example of transgenic bacteria.

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.

Draw a diagram of the microscopic structure of human sperm. Label the following parts in it and write their functions:

1. Acrosome
2. Nucleus
3. Middle piece

Why a transgenic animals so called?