Human Reproduction — BIOLOGY STD 12 Science — Question

In pea plants, the colour of the flower is either violet or white, whereas human skin colour shows many gradations. Explain giving reasons, how it is possible.

Indiscriminate human activities such as alien species invasion, fragmentation and habitat loss have accelerated the loss of biodiversity. Justify by taking one example for each.

Excessive and continuous use of pesticides has resulted in evolution of some new species of pests. Explain what must have led to this. What is this type of evolution called?
OR
Anthropogenic action can hasten evolution. Explain with the help of a suitable example.

State Mendel's law of dominance. How did he deduce the law? Explain with the help of a suitable example.

The enzyme DNA polymerase in E.coli is a DNA dependent polymerase and also has the ability to proof-read the DNA strand being synthesised. Explain. Discuss the dual polymerase.

1. Why must bacterial cells be first made 'competent' in rDNA technology? How is the process carried out?
2. Name the methods by which an alien DNA can be made to enter:

1. A plant cell.
2. An animal cell.

Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled 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, 8 mg/L and 400 mg/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?

Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this the normal function can be restored. An alternate method would be to provide the gene product (protein/ enzyme) known as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.

Give one example of disease caused each by fungi, bacteria and viruses in crop plant.

Define poultry Name any four animals included in poultry.