Human Reproduction — BIOLOGY STD 12 Science — Question

A considerable amount of lactose is added to the growth medium of E.coli. How is the lac operon switched on in the bacteria? Mention the state of the operon when lactose is digested.

A number of passengers were severely burnt beyond recognition during a train accident. Name and describe a modern technique that can help hand over the dead to their relatives.

OR

Following the collision of two trains a large number of passengers are killed. A majority of them are beyond recognition. Authorities want to hand over the dead to their relatives. Name a modern scientific method and write the procedure that would help in the identification of kinship.

At what stage is the mammalian embryo implanted in the uterus?

Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of the observations of the experiment performed by him.

1. At which end he would have loaded the samples and where?
2. Analyse the reason for different positions taken up by the DNA bands.
3. Elaborate the step he would have followed to visualize DNA bands.

1. Match the microbes listed under Column-A with the products mentioned under Column-B.

	Column-A		Column-B
(a)	Penicillium notatum	(i)	Statin
(b)	Trichoderma polysporum	(ii)	Ethanol
(c)	Monascus purpurea	(iii)	Antibiotic
(d)	Saccharomyces cerevisiae	(iv)	Cyclosporin-A

2. Why does ‘Swiss Cheese’ develop large holes?

How do you distinguish between humification and mineralisation ?

Name and explain the surgical method advised to human males and females as a means of birth control. Mention its one advantage and one disadvantage.

Write any four ways used to introduce a desired DNA segment into a bacterial cell in recombinant DNA technology experiments.

When do you describe the relationship between two organisms as mutualistic, competitive and parasitic? Give one example of each type.

Practise drawing various animals and plants.