(a) What is Satellite DNA in a genome?

(b) Explain their role in DNA fingerprinting.

OR

(a) Draw a labelled diagram of replication fork of DNA.

(b) Explain the role of the enzymes involved in DNA replication.

(c) What do you understand by a leading strand and a lagging strand during DNA replication?

(a) Satellite DNA is

• Highly repetitive DNA.
• Short sequences are repeated a large number of times.
• Variable AT-rich repeat unit.
• The monomer length of sequences is between 150 to 400 bp.

(b) DNA fingerprinting is a technique used to identify and analyse the differences in DNA between individuals. It is based on DNA polymorphism. The technique plays a vital role in many processes including:

• Identification of suspects in crime investigations.
• Paternity issues
• Establishing evolutionary links between organisms, etc.
  
  OR
  
  (a)
  

(b) The role of the enzymes involved in DNA replication are 

DNA polymerase III: Helps in the duplication of the DNA strand.
DNA polymerase I: Synthesize short sequences during excision repair, remove RNA primers and fill the gaps between Okazaki fragments in lagging strand. 

DNA ligase: Ligate the breaks in the phosphodiester backbone of DNA. 

Primase: Produces RNA primers

RNase H: Cleaves the RNA of RNA/DNA hybrids. 

DNA helicase : Helicase separates two nucleic acid strands.

In bacteria, gyrase has ATP-dependent activity in the negative super-coiling of circular DNA. It is a type of topoisomerase.
Helix-destabilizing protein: Breaks phosphodiester bond and unwinds the double helix.

(c) The strand that opens in the 3' to 5' direction towards the replication fork is referred to as the lagging strand. The strand that runs in the 5' to 3' direction in the replication fork is referred to as the leading strand.