Question

6. Gel Electrophoresis separates different molecules on the basis of A) Size B) charge C) solubility D) both size and charge 7. Distinguish between leading and lagging strand. 8. How is DNA replication different in eukaryotes from bacteria? 9. Explain semiconservative model of DNA replication 10. Distinguish between helicases and topoisomerases

Answer 1

6. D. Both size and charge
Agarose gel electrophoresis is widely used to separate molecules based upon charge, size and shape.

7. 1. Leading strand synthesis parallel to replication fork.
2. It is continuous strand.
3. Single primer is enough

1. Lagging strand synthesis opposite to replication fork.
2. It is discontinuous strand.
3. Different primer are needed.

8.1. Bacteria is circular DNA so replicated in bidirectional.
2. It has single origin site.
3. Rate - 2000bp/sec

1. Eukaryotic is linear DNA so replicated in unidirectional.
2. It has multiple origin site.
3. Rate - 1000 bp/sec

9. In semi-conservative model after 1st round of replication DNA double helix would be a hybrid of one strand parent [N14] and other is daughter strand [N15]. In 2nd round of replication only half of the new DNA double helices would be hybrids [N14/N15] the other half would be completely new daughter strand [N15/N15].

10. Helicases unwind double-stranded DNA.
Topoisomerases relax double-stranded DNA or relieve superhelical tension.