genotypeProbs: Calculate Probabilities of Unambiguous Genotypes

In polysat: Tools for Polyploid Microsatellite Analysis

Calculate Probabilities of Unambiguous Genotypes

Description

Given an ambiguous genotype and either a data frame of allele frequencies or a vector of genotype probabilities, genotypeProbs calculates all possible unambiguous genotypes and their probabilities of being the true genotype.

Usage

genotypeProbs(object, sample, locus, freq = NULL, gprob = NULL,
              alleles = NULL)

Arguments

object	An object of class "genambig". The Ploidies and PopInfo slots must be filled in for the sample and locus of interest.
sample	Number or character string indicating the sample to evaluate.
locus	Character string indicating the locus to evaluate.
freq	A data frame of allele frequencies, such as that produced by simpleFreq or deSilvaFreq. This argument should only be provided if the selfing rate is zero.
gprob	A vector of genotype probabilities based on allele frequencies and selfing rate. This is generated by meandistance.matrix2 and passed to genotypeProbs only if the selfing rate is greater than zero.
alleles	An integer vector of all alleles. This argument should only be used if gprob is also being used.

Details

This function is primarily designed to be called by meandistance.matrix2, in order to calculate distances between all possible unambiguous genotypes. Ordinary users won't use genotypeProbs unless they are designing a new analysis.

The genotype analyzed is Genotype(object, sample, locus). If the genotype is unambiguous (fully heterozygous or homozygous), a single unambiguous genotype is returned with a probability of one.

If the genotype is ambiguous (partially heterozygous), a recursive algorithm is used to generate all possible unambiguous genotypes (all possible duplications of alleles in the genotype, up to the ploidy of the individual.)

If the freq argument is supplied:

The probability of each unambiguous genotype is then calculated from the allele frequencies of the individual's population, under the assumption of random mating. Allele frequencies are normalized so that the frequencies of the alleles in the ambiguous genotype sum to one; this converts each frequency to the probability of the allele being present in more than one copy. The product of these probabilities is multiplied by the appropriate polynomial coefficient to calculate the probability of the unambiguous genotype.

p = ∏_(i=1)^n f_i^(c_i) * (k-n)!/(∏_(i=1)^n c_i!)

where p is the probability of the unambiguous genotype, n is the number of alleles in the ambiguous genotype, f is the normalized frequency of each allele, c is the number of duplicated copies (total number of copies minus one) of the allele in the unambiguous genotype, and k is the ploidy of the individual.

If the gprob and alleles arguments are supplied:

The probabilities of all possible genotypes in the population have already been calculated, based on allele frequencies and selfing rate. This is done in meandistance.matrix2 using code from De Silva et al. (2005). Probabilities for the genotypes of interest (those that the ambiguous genotype could represent) are normalized to sum to 1, in order to give the conditional probabilities of the possible genotypes.

Value

probs	A vector containing the probabilities of each unambiguous genotype.
genotypes	A matrix. Each row represents one genotype, and the number of columns is equal to the ploidy of the individual. Each element of the matrix is an allele.

Author(s)

Lindsay V. Clark

References

De Silva, H. N., Hall, A. J., Rikkerink, E., and Fraser, L. G. (2005) Estimation of allele frequencies in polyploids under certain patterns of inheritance. Heredity 95, 327–334

See Also

meandistance.matrix2, GENLIST

Examples

# get a data set and define ploidies
data(testgenotypes)
Ploidies(testgenotypes) <- c(8,8,8,4,8,8,rep(4,14))
# get allele frequencies
tfreq <- simpleFreq(testgenotypes)

# see results of genotypeProbs under different circumstances
Genotype(testgenotypes, "FCR7", "RhCBA15")
genotypeProbs(testgenotypes, "FCR7", "RhCBA15", tfreq)
Genotype(testgenotypes, "FCR10", "RhCBA15")
genotypeProbs(testgenotypes, "FCR10", "RhCBA15", tfreq)
Genotype(testgenotypes, "FCR1", "RhCBA15")
genotypeProbs(testgenotypes, "FCR1", "RhCBA15", tfreq)
Genotype(testgenotypes, "FCR2", "RhCBA23")
genotypeProbs(testgenotypes, "FCR2", "RhCBA23", tfreq)
Genotype(testgenotypes, "FCR3", "RhCBA23")
genotypeProbs(testgenotypes, "FCR3", "RhCBA23", tfreq)

polysat documentation built on Aug. 23, 2022, 5:07 p.m.