I've been looking at some sequenced exomes and found an interesting point mutation that causes a Proline-to-Leucine amino acid change in the protein. This seems like it could have a big impact on the protein's functionality but before I go any further I want to explore whether or not the variant is a sequencing artifact.
I looked at the coverage for this particular region of the genome and found that in some samples, the point mutation is seen in every single read covering the base in question while in others the point mutation is seen in approximately half of the reads. In all my samples, the base in question is covered by at least 15 separate reads but usually its more than 20.
My primary question is: how should I interpret the cases where the point mutation is seen in some but not all of the reads covering its location?
I'm also interested in any suggestions/advice on the more general topic of determining whether or not the mutation I've found is a sequencing artifact.