Relationship & Inbreeding

1. Relationship & Inbreeding Napapan Piyasatian

2. Outline • What is relationship? • How is relationship computed? • What is inbreeding? • How is inbreeding computed? • What is relationship with inbreeding? • How is relationship with inbreeding computed?

3. Relationship • Inbreeding occurs when related animals are mated • Outbreeding occurs when less related animals are mated • What is meant by ‘relationship’? • How is it measured?

4. Relationship • Measures the probable proportion of genes that 2 individuals have in common above the average of the population at some point in time • Probable proportion:element of chance • Above the average of the population:relationship is NOT an absolute measure • At some point in time: increase the relative nature of relationship

5. Relationship • What would be the relationship between a sire and its offspring? • Proportion of genes that are expected to be in common • Offspring = + http://www.gifshare.com/gif/7851/sperm

6. Relationship • What is the relationship between humans and chimpanzees? • 97% humans’ DNA = Chimps’ DNA • 99% of all human DNA is the same • Above the average of human populations • Above the average of mammal populations http://animal.discovery.com/mammals/chimpanzee/

7. Relationship - Are your parents related? • Relative to some point in time • Pick year 0 • Unrelated parents implies unique people in each pedigree • Number of ancestors in a generation • = 2n • 2 parents, 4 grandparents, 8 great-grandparents, etc.

8. Relationship - Are your parents related? • Number of ancestors in a generation • = 2n • About 66 generations since year 0 (1983/30=66.1) • 266 = 7.4 x 1019 people in each parent’s pedigree in year 0 • Some of the people must be the same

9. Relationship - Are your parents related? • Relationship from > 5 generations ago • Contribute little to relationship value • Usually the same point in time is the last 5 generations or less • Only 25 = 32 people

10. Other relationship definition • Relationship measures the expected genetic correlation between the breeding values of animals with this relationship. • This meaning is used in BLUP equations

11. Types of relationship • Direct relationship – gene passed from one animal to the other • Parent & offspring • Grandparent & offspring • Indirect relationship – common ancestor • Sibs • Cousins

12. Calculate relationship, RXY • Sewall Wright procedure (1921) • Create an arrow diagram from the block pedigree • Identify all paths that contribute to relationship, including all direct & collateral relationships • Determine all contribution of each path and calculate relationship as the sum of each path’s contribution • Without inbreeding, RXY = sum of all contributions from all paths

13. Sire Offspring Dam 1. Create an arrow diagram

14. 2. Identify all paths 1 • Trace path starting at one individual and ending at the other • Always start tracing against the arrows • Arrow can change direction once while tracing the path (collateral relationship) but need not change direction (direct relationship) • Any animal can occur only once in a given path (important to remember this rule when animals are inbred) • Include all paths that contain a new sequence of individuals or one different individual

15. Path Sire Offspring Sire Offspring Dam 2. Identify all paths 2 Paths for relationship between sire and offspring

16. Contribution = (½)n (½)1 = ½ Path Sire Offspring 3. Determine contribution of each path

17. Path Sire Offspring 4. Sum of all contributions • Contribution = (½)n • (½)1 = ½ • RXY= ½