Human Reproduction — BIOLOGY STD 12 Science — Question

A haemophilic father can never pass on the gene for haemophilia to his son. Explain.

What is the role of cervix in the human female reproductive system?

Three water samples namely river water, untreated sewage water and Secondary effluent discharged from Sewage treatment plant were subjected to BOD test. The samples were labelled in A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20 mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

What is RCH programme ?

Suggest four important steps to produce a disease resistant plant through conventional plant breeding technology.

Name an opioid drug and its source plant. How does the drug affect the human body?

Name any four mammals that lived in South America before continental drift.

Mention any two ways how opiate narcotics affect human body.

Describe the structure of a nucleosome.

With the help of one example, explain the phenomena of co–dominance and multiple allelism in human population.