Question

1. Answer the following questions from your knowledge on the DNA analysis and amplification lab experiment.

a) What molecular mechanism is thought to operate in vivo during DNA replication with the result that dinucleotide repeats become highly polymorphic loci?

b) When it comes to PCR reactions that involve a DNA target containing a dinucleotide repeat, would you expect to see any additional minor PCR products in addition to the principal product on the PAGE get? Explain your answer

c) What main advantage does a microsatellite have over using a single nucleotide polymorphism (SNPs) as a genetic marker?

Answer 1

Let's s get to the question directly since it does not need any introduction.

1. Initially, the simplest mechanism of DNA replication seemed to be the continuous growth of both new strands, nucleotide by nucleotide, at the replication fork as it moves from one end of a DNA molecule to the other. But because of the antiparallel orientation of the two DNA strands in the DNA double helix, this mechanism would require one daughter strand to polymerize in the 5′-to-3′ direction and the other in the 3′-to-5′ direction. Such a replication fork would require two different DNA polymerase enzymes. One would polymerize in the 5′-to-3′ direction, where each incoming deoxyribonucleoside triphosphate carried the triphosphate activation needed for its own addition. The other would move in the 3′-to-5′ direction and work by so-called “head growth,” in which the end of the growing DNA chain carried the triphosphate activation required for the addition of each subsequent nucleotideAlthough head-growth polymerization occurs elsewhere in biochemistry, it does not occur in DNA synthesis; no 3′-to-5′ DNA polymerase has ever been found.

2. Chances of forming minor addition are less. PCR Products accepts one or more DNA sequence templates and two primer sequences. Searches can be made for perfectly matching primer annealing sites that can generate a PCR product. Any resulting products are sorted by size, and they are given a title specifying their length, their position in the original sequence, and the primers that produced them. Amplyfing non-specifc products or primers are hybridizing with each other (primer dimers, which will appear as a low molecular weight band) are the main causes . If by some reason the target sequence is present in low quantity in that particular isolate, the primers will be more available to bind unspecific regions.

3.Microsatellite loci are standard genetic markers for population genetic analysis, whereas single nucleotide polymorphisms (SNPs) are more recent tools that require assessment of neutrality and appropriate use in population genetics. SNP markers provided estimates of population genetic parameters consistent with those from microsatellite data, and their low back mutation rates may result in reduced propensity for error in estimation of population parameters. The main advantage is that Microsatellite markers produces little or no mutation at all in sub population. While SNP is opposite to this.