Inbreeding

Question 1

Define the term Inbred

Answer 1

The mating of related individuals which tends to increase the numbers of homozygotes.

Question 2

Give 3 examples of inbreeding in Royal Famillies.

Answer 2

• Diana and Charles: both share lineage with Edward III. Diana 4000 lines, Charles 3000.
• Spanish Royal Family: Alfonso has only 8 ancestors (expected is 128)
• Pharaoh Tutankhamen parents were siblings

Question 3

Define the term Identical by descent

Answer 3

The passing on of alleles that are identical (inherited from the same person) due to inbreeding

Question 4

Define the Inbreeding Coefficient

Answer 4

the probability that a pair of alleles at a locus will be identical t by descent.

Question 5

What is a characteristic feature of an inbred Pedigree?

Answer 5

Every inbred Pedigree has a loop that links the two mates through their shared ancestors

Question 6

What is the formula for Inbreeding Coefficient?

Answer 6

F = ∑ N(0.5)^n

N = number of loops 
n = number of ancestors per loop

Question 7

Define Inbreeding Depression

Answer 7

A reduction in fitness associated with inbreeding.

Question 8

Give an example of Inbreeding Depression

Answer 8

Collie dogs: intense inbreeding over many generations to amplify and preserve favourable characteristics- Congenital Myopathy

Question 9

Give another example of Inbreeding Depression

Answer 9

King Charles Spaniels- Syringomyelia, brains are too big for skulls

Question 10

Give an example of how inbreeding has led to a loss of diversity.

Answer 10

The Arion ater Slug- it is hermaphrodite. More self-fertilisation occurs in Scotland where environment is homogenous. Less variation in slug colour- all appear black

Question 11

Give an example of Inbreeding depression in humans.

Answer 11

VLINCL is a rare recessive disease but has relatively high incidence in Finnish families (well documented Pedigrees). The allele can be traced back to one het male in 17th C.

Question 12

Give the two ways in which the extent of inbreeding can be measured

Answer 12

• The inbreeding coefficient

- Runs of Homozygosity

Question 13

What are RoH?

Answer 13

Regions of the genome where the copies inherited from parents are identical creating a run of homozygous variants

Question 14

How can RoH be used to asses Inbreeding?

Answer 14

The longer the length of the run the greater the extent of inbreeding

Question 15

Why does a long RoH suggest inbreeding?

Answer 15

There is reduced recombination in related people hence conserved blocks of homozygosity.