After google search and reading some articles, I still have no idea how to calculate genotype likelihood for a locus using quality scores for reads using simple probability. The probability math symbols in those articles are hard for me to understand how to do the calculation.

For example, for a locus, the reference sequence has T. There are 6 reads, 4 reads have T and 2 reads have G (with quality score = 10) at that locus.

If the true genotype of this locus is [T,T], the question is how does one calculate the probability of this genotype at this locus, i.e. P(D | [T, T])? D for the given data of reads.