In population genetics, Sewall Wright's coefficient of relationship or coefficient of relatedness or relatedness or r is the probability that at a random locus, the alleles there will be identical by descent or autozygous. Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist Probability is the likelihood or chance that something is the case or will happen In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms Alleles have identity by type (IBT if they have the same phenotypic effect.
For example, in a diploid species (e. "Haplo" redirects here For the fictional character see The Death Gate Cycle. g. all mammals), the coefficient of relationship between parent and offspring is 0. 5, meaning half of the offspring's genome comes from that parent. [1] Or, more precisely said, half the genomes are identical by descent.
Some other relatedness examples: (assuming no consanguinity, for diploid species unless noted otherwise)
| r | relationship |
|---|---|
| 0. Consanguinity (" con- (with sanguine (blood -ity" refers to the property of being from the same Lineage as another person 5 (½) | parent-offspring |
| 0. 25 (¼) | grandparent-grandchild |
| 0. 125 (⅛) | great grandparent-great grandchild |
| 1 | identical twins |
| 0. 5 (½) | full siblings |
| 0. 25 (¼) | half siblings |
| 0. 03125 (1/32) | second cousins[2] |
| 0. 75 (¾) | full hymenoptera sisters[3] |
Some of these definitions of r are tricky to calculate. Hymenoptera is one of the larger orders of Insects comprising the sawflies, Wasps Bees and Ants The name refers to For example, consider that you are one of a family of half brothers with the same mother but different fathers. Call rm the coefficient of matrilineal relatedness and call rp the coefficient of patrilineal relatedness. What is the coefficient of relatedness to each of your half brothers?
rm=0. 5 as it does for normal siblings, since there is a 1 in 2 chance that you and your half brother developed from eggs from harboring the same haploid genome selected during maternal meiosis. But rp=0 since there is no chance that any two brothers inherited the same allele from different fathers by descent. The average of these rs equals 0. 25, as we see above. You and your half brother are one quarter genetically identical by descent.
In the example above, the differentiation between maternal and paternal coefficients of relatedness was made in order to introduce the phenomenon of imprinting, or parent-specific gene expression into the calculation of r.
To illustrate how an imprinting turns normal siblings into half siblings, consider that you are one of a cadre of full siblings. What is your coefficient of relatedness to one of your siblings at an imprinted locus in a maternally inherited allele? (Maternally inherited alleles are called "madumnal," and paternally inherited alleles are called "padumnal". )
The value of r at this imprinted locus is equal to the value of r for the entire genome of the half brothers. For the brothers above, rm=0. 5 and rp=0. For the madumnal locus in the family of full siblings rm=0. 5 too, since all expression is from the mother's allele. Normally, rp=0. 5 for full siblings with the same father, but the effect of imprinting is to negate paternal expression, hence rp=0. Therefore you and your full siblings resemble half-siblings at imprinted loci.
See also
References
- Sewall Wright, (1922). In Genetics, Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals There are a few definitions of Inclusive fitness (IF but one (that according to Oli 2003 is not consistent with W From the time of antiquity field biologists have observed that some organisms tend to exhibit strategies that favor the reproductive success of their relatives even at a cost to their own survival Sewall Green Wright ( December 21, 1889 – March 3, 1988) was an American Geneticist Coefficients of inbreeding and relationship. American Naturalist 56:330-338
- ^ Kin Selection. American Naturalist is a monthly Scientific journal, founded in 1867 and associated with the American Society of Naturalists. Benjamin/Cummings.
- ^ Relatedness Part 2. Retrieved on 2007-11-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1034 - Máel Coluim mac Cináeda, King of Scots dies Donnchad, the (excerpted from The Selfish Gene, Richard Dawkins)
- ^ Effects of Insemination Quantity on Honey Bee Queen Physiology. NIH PLoS ONE. Retrieved on 2007-11-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1034 - Máel Coluim mac Cináeda, King of Scots dies Donnchad, the (In haplodiploid honeybees, supersisters are daughters of the same queen who has been inseminated by a single drone. )