Human Reproduction — BIOLOGY STD 12 Science — Question

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 visualise DNA bands.

1. Mention the exact location or the site in a flowering plant, where the following developments take place:

1. Deposition of sporopollenin.
2. Triple fusion.
3. Release of male gametes.
4. Megasporogenesis.

2. Draw a labelled diagram of a male gametophyte of an angiosperm.

To which category of cells do B-cells and T-cells belong? How do they differ from each other with reference to their formation and response to antigens?

Selecting the recombinants becomes cumbersome when antibiotic is inactive- explain.###How can we distinguish between recombinant and non recombinant plasmid? Illustrate.

For flower colour in pea, the allele for purple flower (P) is dominant to the allele for white flower (p). A purple flowered plant therefore could be of genotype PP or Pp. What genetic cross would you make to determine the genotype of a purple flowered plant? Explain how your cross gives you the correct genotype of the purple flowered plant?

Explain the different organs of flower by drawing longitudinal section (L.S.) of a typical flower.

Explain biodiversity loss due to alien species invasions.###Among the reasons of biodiversity loss, how does extinction of indiginous species is carried out by invation of allian species? Explain.

Mention the difference between spermiogenesis and spermiation.

Explain the role of the enzyme EcoRI in recombinant DNA technology.

Organisms at a higher trophic level have less energy available. Comment.