Principles of Inheritance and Variations — BIOLOGY STD 12 Science — Question

A pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage?

Name a disorder, give the karyotype and write the symptoms where a human male suffers as a result of an additional X–chromosome.

How does the sperm penetrate through the zona pellucida in human ovum?

Draw a vertical section of a maize grain and label (i) pericarp, (ii) scutellum, (iii) coleoptile and (iv) radicle.

Answer the following questions:
Mature seeds of legumes are non-albuminous. Then, can it be assumed that double fertilisation does not occur in legumes? Explain your answer

Name the biological products made in transgenic animal to treat emphysema. Explain.

Explain the status, function and percentage of RNA polymerase enzyme found in eukaryotic cells.

If there would exist only 10000 ants species instead of 20000 species on this planet how would it be affect our life?

Fulfillment of a, b, c and d in the table given below.

S.No.	Name of Drug	Plant source	Name of affected part
1	a	Popy plant	B
2	Marijuana	c	d

What is a vaccine? How do they act to provide long term immunity to an individual, who is vaccinated?

OR

Write the events that take place when a vaccine for any disease is introduced into the human body.

OR

How does a vaccine for a particular disease immunise the human body against that disease?

OR

Name and explain the type of immunity that is provided by injecting microbes deliberately during immunisation into the human body.