5) Using the Fnu4HI CAPS assay, you genotype yourselfor at TAS2R38 and learn tha

Question

5) Using the Fnu4HI CAPS assay, you genotype yourselfor at TAS2R38 and learn that you are homozygous for the AVI/AVI allele. Next, you decide to genotype a sample of DNA extracted from a Neanderthal bone You do not wear gloves while setting up the PCR reaction. You do not perform a negative control reaction. You digest the PCR reaction with Fnu4HI and obtain the result shown below. What can you conclude about the genotype of the Neanderthal (AVI/AVI, AVI/PAV, PAVIPAV)? Explain your answer. 300b 200b 100b 50bp Lane 1, 100-bp ladder. Lane 2, Neanderthal sample.

Explanation / Answer

The DNA of a sample contains alleles of the genes which compose its genome. These alleles can be similar in nature or different, thus making the organism either homozygous or heterozygous, respectively. When this DNA is resolved onto agarose gel, it gives the pattern of bands, where each band represents a type of allele when a specific primer-oriented PCR is conducted. Thus, a single band would correspond to a homozygous genotype whereas the presence of two bands would correspond to a heterozygous genotype.

Here, it can be clearly seen from the image that there are two bands present in the gel-picture which undoubtedly correspond to two types of alleles. Thus, the genotype of the organism under consideration is heterozygous in nature i.e. AVI/PAV.

As the information suggests that the experimenter performed the experiment bare handed, it might be possible that there would have been human-contamination in the sample and that is why two bands appeared in the gel. Thus, the information is also suggestive that the genotype of the experimenter is homozygous for AVI/AVI genotype, thus suggesting that the genotype of the sample should be only PAV/PAV in nature.

Thus, these set of data suggest that the genotype of the sample should be originally PAV/PAV and the appearance of two bands in the agarose gel can be attributed to contamination from the hands of the experimenter.

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