Question

estion 11 A drop of blood from the perpetrator lok at the scene of a crime was and how the bodas e themelet e prema chain reaction (PCR) thai targeted and amplified 3 gone out this scenario complete with a) Which suspect (suspect A, B or C) was likely at the scene of the crime? Explain your response b) What is the size of the longest DNA fragment in lane 2 (in base pairs)?

Answer 1

a). Answer:- Suspect A was likely to be present at crime scene according to Polymerase Chan Reaction (PCR) results shown in figure.

Explanation:- DNA sample of suspect A exactly matched with the DNA sample found at crime scene. We can easily see marker of same sizes found in both DNA sample.

b). Answer:- About 6500base pairs. Size can be matches with DNA ladder of lane 5, largest sized DNA of lane 2 lie almost between 6000bp to 7000bp.

c). Answer:- Following are the three steps occur during each cycle of PCR which also likely to happen during replication process in vivo :-

Step 1: Denaturation- As in DNA replication, the two strands in the DNA double helix also called template DNA, get separated for binding of primer by breaking Hydrogen bonds between bases of these two strands.

Step 2: Annealing- Primers bind to each seprated single stranted target DNA at sequences of 3' end which is complementary to primer sequences and initiate polymerisation.

Step 3: Extension- New strands of DNA are made using components of Solutions that is all four deoxynucleotides (dNTPs) in the presence of DNA Polymerase enzymes at each single stranded template DNA and making it Double stranded.

Each double stranded DNA synthesized at 3rd step of each cycle act as template for 1st step of next succesive cycle thus, results in huge amount of amplified DNA at the end of PCR reactions.