How to obtain likelihood ratios using SNPs

To find the likelihood ratio using SNPs, the probability of genotype match is calculated, which is then used to calculate the likelihood for a specific hypothesis (e.g. the hypothesis that a person has a specific parent-child relationship).Specifically, the following steps are performed.

SNP data collection: collect SNP data from the DNA of the parent-offspring candidates.
Match probability calculation: calculates the SNP match probability between parent-offspring candidates.
Likelihood ratio calculation: computes the likelihood ratio by comparing the likelihoods of the parent-offspring and non-parent-offspring relationship hypotheses.
For example, if the probability that the SNPs match is p and the probability that they do not match is q, the likelihood ratio (LR) is expressed as p/q.SNP data collection: collect SNP data from the DNA of the parent-offspring candidates.
Match probability calculation: calculates the SNP match probability between parent-offspring candidates.
Likelihood ratio calculation: computes the likelihood ratio by comparing the likelihoods of the parent-offspring and non-parent-offspring relationship hypotheses.
For example, if the probability that the SNPs match is p and the probability that they do not match is q, the likelihood ratio (LR) is expressed as p/q.

Specific examples are given here.

Assumptions:
Allele of SNP A: parent ‘AA’, child ‘AA’.
Frequency of allele A in population:.Assumptions:
Allele of SNP A: parent ‘AA’, child ‘AA’.
Frequency of allele A in population:.

likelihood in the presence of a parent-child relationship:.1. likelihood in the presence of a parent-child relationship:.

If the parent is ‘AA’, the probability that the child is also ‘AA’ is 1.

2. likelihood of no parent-child relationship:.

The probability that a child is ‘AA’ depends on how common allele A is in the population.

3. calculation of the likelihood ratio (LR):

The likelihood ratio of 100 indicates that the hypothesis of a parent-child relationship is 100 times more favored than the hypothesis of no parent-child relationship.

If multiple SNPs are used, a similar calculation is performed for each SNP and their likelihood ratios are multiplied to obtain the final likelihood ratio.

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