How many short tandem repeat (STR) loci would need to be analysed before you would consider a DNA match to be statistically valid? Justify your answer.

How many STR(short tandem repeats) loci are required to assist in solving a crime in a series of citites of increasing population size such as Canberra, Papua New Guinea and Indonesia using an online STR database

Check list of the minimum statistical analysis required

• Standard Statistics: Number of alleles Na, observed heterozygosity HO, expected heterozygosity

HE for all loci. Also report the mean of these values over the loci.

• DNA Profile probabilities DPP, across all 15 loci for two different individuals.

• Cumulative PI for increasing combinations of the 15 loci.

• Compute the odds for all probabilities that you calculate (e.g. DPP and PI).

Assess whether the STR database populations approximate HWE (F=0).

• Compute the degree of differentiation (FST) among the populations in the database.

Biology Multiple Choice Questions!!

I know that power analysis is the statistically valid way toensure you use the correct numer of samples or repeats in anexperiment. But I have never seen any biologist actually conduct apower analysis. Mostly, researchers seems to use a rule of thumb(three technical, three biological replicates is a common one).

Should I be doing a power analysis each time I design anexperiment, or can I just use one of the common biology rules ofthumb? If not, what are the consequences for the validity of myresults? And is there a situation where I will be required to usepower analysis, which makes it advantageous to get used to doing itnow?