MSc Thesis
In the present study, 100 unrelated father-son buccal swab sample pairs from consented
Tanzanian population were examined to establish mutation rates using 17 Y-STRs loci
DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a,
DYS385b, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, and Y-
GATA-H4 of the AmpFlSTRYfiler kit used in forensics and paternity testing. Prior to 17
Y-STRs analysis, father-son pair biological relationships were confirmed using 15
autosomal STRs markers and found to be paternally related. A total of four single repeat
mutational events were observed between father and sons. Two mutations resulted in the
gain of a repeat and the other two resulted in a loss of a repeat in the son. All observed
mutations occurred at tetranucleotide loci DYS389II, DYS385a and DYS385b. The locus
specific mutation rate varied between 0 and 1.176 x10 -3 and the average mutation rate of
17 Y-STRs loci in the present study was 2.353x10 -3 (6.41x10 -4 - 6.013x10 -3 ) at 95% CI.
Furthermore the mean fathers’ age with at least one mutation at son’s birth was 32 years
with standard error 2.387 while the average age of all fathers without mutation in a
sampled population at son’s birth was 26.781 years with standard error 0.609. The results
shows that fathers’ age at son’s birth may have confounding effect on Y-STRs mutation
rate analysis though this age difference is statistically not significant using un paired
samples t-test (p = 0.05). As a consequence of observed mutation rates in this study, the
precise and reliable understanding of mutation rate at Y chromosome short tandem repeats
loci is necessary for a correct evaluation and interpretation of DNA typing results in
forensics and paternity testing involving males. The criterion for exclusion in paternity
testing should be defined, so that an exclusion from paternity has to be based on exclusion
constellations at the minimum of two 17 Y-STRs loci.
Tanzania Government Chemist Laboratory Agency (GCLA)