Evolution — BIOLOGY STD 12 Science — Question

Meiotic division during oogenesis is different from that in spermatogenesis. Explain how and why?

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

Explain the process of replication of a retrovirus after it gains entry into human body.

What is decomposition? Write the various steps of this process and give a diagrammatic representation of the decomposition cycle in a terrestrial ecosystem.

What do you understand by crossing over? Describe the mechanism of crossing over with suitable diagram.

Define an operon. Giving an example, explain an Inducible operon.

A child suffering from thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby.

1. What is thalassemia?
2. How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.
3. List the values your counselling can propagate in the families.

Identify a, b and c in the table given below:

S. No.	Pattern of inheritance	Monohybrid F1 phenotypic expression
(i)	Co–dominance	a
(ii)	b	The progeny resembled only one of the parents.
(iii)	Incomplete dominance	c