Mating System

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Mating System I

Fun with Nonrandom Mating: Our Topics
• • • • • • Classification of mating systems Definitions Consequences of inbreeding Inbreeding in pedigrees Regular systems of inbreeding Estimation of mating system parameters

Classification of Mating Systems
• Random mating • Assortative mating . . . may be:
– Phenotypic or genotypic – Positive or negative (disassortative)

• Inbreeding
– Mating among relatives (more frequently than would occur at random) – Special type of genotypic assortative mating

1

Classification of Mating Systems (continued)
• Mixed mating model (s + t = 1)
s proportion of progeny produced by selfing t proportion of progeny produced by outcrossing

• In nature there exists a dichotomy
– Inbreeders – Outcrossers – ( e.g., few organisms have s

1/2 )

Example of Inbreeding in a Pedigree
Individual 1 A1A1 α1α2 Individual 2 A1A2 α3α4 Individual 3 A3A3 α5α6

Individual 4

Individual 5

Individual O
•Ai indicates allelic state (i.e. an allele’s genotype) •α1 . . . α6 uniquely identify the 6 alleles in Individuals 1-3 •α1 . . . α6 imply nothing about allelic state (i.e. allele’s genotype)

A Possible Outcome for Individual “O”
Individual 1 A1A1 α1α2 Individual 2 A1A2 α3α4 Individual 3 A3A3 α5α6

Individual 4

Individual 5

Individual O α3α3 A1A1
•DEFINITION: Autozygous means alleles are “identical by descent” •Individual O is “autozygous” (α3α3) •Individual O is homozygous (autozygotes are always homozygotes)

2

A Different Possible Outcome for “O”
Individual 1 A1A1 α1α2 Individual 2 A1A2 α3α4 Individual 3 A3A3 α5α6

Individual 4

Individual 5

Individual O α4α4 A2A2 •O is autozygous (α4α4) •O is homozygous

Yet Another Possible Outcome for “O”
Individual 1 A1A1 α1α2 Individual 2 A1A2 α3α4 Individual 3 A3A3 α5α6

Individual 4

Individual 5

Individual O α3α4 A1A2
•O is allozygous (α3α4, i.e. NOT autozygous) •O is heterozygous

One Final Example Outcome for “O”
Individual...
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