Question

DNA sequencing by the chain-termination method utilizes DNA polymerase I to make a complementary copy of the target or template DNA molecule. A reaction with a 20 bp template and dideoxyadenosine nucleotides as terminators results in the production of a 5 bp fragment. Based on this result, we can conclude that the template contains A) a cytosine at position 5. B) a thymine at position 5. C) a cytosine at position 16. D) a thymine at position 16

Answer 1

Answer:

D) a thymine at position 16

Explanation:

The chain termination method (Sanger sequencing), is a sequencing technique used to determine the nucleotide sequence of a specific fragment of DNA. The classical method has three steps: 1- the target DNA fragment to be sequenced is used as a template for chain-termination PCR technique where modified deoxyribonucleotides (ddNTPs) are added to the PCR reactions to be incorporated by the DNA polymerase during in vitro DNA replication, 2-the DNA fragments of different sizes are separated by electrophoresis, and 3-determination of the DNA sequence by observing the identity of the terminal ddNTP in each band of the electrophoresis gel. For example, if the bottom band in the electrophoresis gel colocalizes in the column with ddATP as terminator, then this fragment finishes with ddATP, which means that the last nucleotide from the 5' end is Adenine.