Human Health and Disease — BIOLOGY STD 12 Science — Question

The following diagrams are the age pyramids of different populations. Comment on the status of these populations.

1. Describe the characteristics a cloning vector must possess.
2. Why DNA cannot pass through the cell membrane? Explain. How is a bacterial cell made ‘competent’ to take up recombinant DNA from the medium?

Describe in detail the origin and evolution of human?

Recombinant DNA vectors are typically attenuated viruses or bacteria that are unrelated to the pathogen of interest.
These vectors can penetrate human cells and often replicate within them, but do not cause disease in the host.


i. A recombinant vector with a gene of interest inserted within the gene of a-galactosidase enzyme, is introduced into a bacterium. Explain the method that would help in selection of recombinant colonies from non-recombinant ones.
ii. Why is this method of selection referred to as insertional inactivation?

Answer the following questions:
Draw a diagrammatic sectional view of the female reproductive system of human and label the parts:

1. Where the secondary oocytes develop.
2. Which helps in collection of ovum after ovulation.
3. Where fertilisation occurs.
4. Here implantation of embryo occurs.

State the similarity and differences between geitonogamy and xenogamy. Why do cleistogamous flowers assure seed sets?

(i) Write full name of AIDS.
(ii) Write four ways of transmission of HIV infection.
(iii) Write a way to prevent HIV infection.

DNA separated from one cell, when introduced in another cell, is able to bestow some of the properties of the former to the latter. What is this change called in technical terms? Describe the experiment evidences which led to the discovery of the above phenomenon.

Explain the two complexities that are observed in the process of transcription in eukaryotes and not in prokaryotes.

“Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel”. Explain.