A normal couple has a colour-blind child, whereas a child suffering from thalassemia is born to normal parents. Compare the pattern of inheritance of these two traits in the said cases. State the reasons how is it possible.

OR

(a) State the reasons for which Hershey and Chase carried out their

experiments.

(b) Answer the following questions based on the experiments of

Hershey and Chase:

(i) Name the different radioactive isotopes they used, and explain how they used them.

(ii) Why did they need to agitate and spin their culture?

(iii) Write their observations and the conclusions they arrived at.

Colour blindness is a sex linked recessive disease that means the progeny, if it is a girl, both the father and the mother to be a carrier. However if the father was a carrier, he’d be colour-blind as well since males have only one X chromosome. Therefore, the colour-blind child born was male. If both parents were normal, this means that the mother was a carrier.

Thalassemia ia an autosomal recessive disorder. For the child to have the disorder, both parents need to have been a carrier of the faulty gene.

OR

a) Hershey and Chase carried out their experiments to figure out if it was indeed DNA that was the genetic material.

b) i) They used P³² and S^35. The radioactive isotope of phosphorous was used to label DNA and the radioactive isotope of sulphur was used to label the protein capsule of the bacteriophage.

ii) The culture needed to be spun and agitated so as to remove the virus coat from bacteria.

iii)

• S³⁵ was detected in the supernatant.

• Radioactive P³² was detected in the cell.

• The proteins did not enter the bacteria from the viruses therefore it was concluded that DNA is the genetic material that got passed from the virus to the bacteria.