Organisms and Populations — BIOLOGY STD 12 Science — Question

Write a note on barrier method: (i) Condoms (ii) Diaphragm, cervical caps, vaults

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.

Explain the unit of transcription and gene.

The corona radiata of an ovum acts as a barrier for the penetration of sperms. How do sperms overcome this barrier?

When Morgan conducted dihybrid cross on Drosophila like Mendel did with pea plants, the F₂ ratio deviated significantly from that of Mendel's F, ratio. Write the explanation Morgan and his group gave to the observations they obtained from their experiment.

Given below are the events that are observed in an artificial hybridisation programme. Selection of parents → Emasculation → Bagging → Collection of pollen from other male plant → Dusting of pollen on stigma — Rebagging.
While, planning for crop improvement involving dioecious plants, which of the above mentioned steps would not be relevant?

Given below is the representation of amino acid composition of the relevant translated portion of b-chain of haemoglobin, related to the shape of human red blood cells.

What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?

Amazonian rain forest has the greatest biodiversity on earth. List any two hypothesis that are proposed by the biologists to account for the greater biological diversity.

Enzymes play an important role in detergents that we use for washing clothes. These enzymes are obtained from some unique microorganisms, enlist atleast two of them. Also name the enzyme.

Explain Parasitism and co-evolution with the help of one example of each.