Human Reproduction — BIOLOGY STD 12 Science — Question

Unless the vector and source DNAs are cut, fragments separated and joined, the desired recombinant vector molecules cannot be created.

1. How are the desired DNA sequences cut?
2. Explain the technique used to separate the cut fragments.
3. How are the resultant fragments joined to the vector molecule?

A person in your colony has recently been diagnosed with AIDS. People/residents in the colony want him to leave the colony for the fear of spread of AIDS.

1. Write your view on the situation, giving reasons.
2. List the possible preventive measures that you would suggest to the residents of your locality in a meeting organised by you so that they understand the situation.
3. Write the symptoms and the causative agent of AIDS.

The following is the illustration of the sequence of ovarian events (a – i) in a human female.

Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.

The graph given below shows the variation in the levels of ovarian hormones during various phases of menstrual cycle:

Identify ‘A’ and ‘B’.

Shown above is the electron micrograph (EM) picture of 'beads-on-string'.

1. Identify and explain the detailed structure of a bead with the help of a labelled diagram.
2. Describe the packaging of 'beads-on-string'in a eukaryotic cell.

State and explain with the help of a cross, the law of segregation as proposed by Mendel.

Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal say horse.

i. How and why is charging of tRNA essential in the process of translation?
ii. State the function of ribosome as a catalyst in bacteria during the process of translation.
iii. Explain the process of binding of ribosomal units to mRNA during protein synthesis.

Describe in detail about food chain and food web existing in an ecosystem.