multifactorial inheritance

Question 1

multifactorial disorders

Answer 1

-many (greater then or = to 3) genes plus environmental trigger/s
-accounts for the vast majority of late onset inherited diseases
-sporadic occurence in pedigree
-incidence not = between sexes
-difficult to eradicate (hard to identify factors)

Question 2

quantitative or complex traits

Answer 2

-qualitative: defined by presents and absence of a trait (red or black… got it or dont)
-quantitative: different severities of effect

Question 3

canine malignant lymphoma

Answer 3

-progressive cancer of lymph nodes
-genes plus triggers: herbicide, pesticide, paints, solvents, flea and tick meds
-when exposed greater risk

Question 4

cancer in eyes of hereford cattle

Answer 4

-lack of pigmentation around eye
-sunlight
-might be linked to the white face gene

Question 5

diabetes in dogs

Answer 5

-2-5F:1M
-exacerbated by pregnancy
-example of gender imbalance
-some dogs are more prone but less prone dogs can get it as well

Question 6

indicators of multifactorial inheritance

Answer 6

-late onset
-sporadic occurrence in pedigree
-incidence not equal between sexes

Question 7

osteochondrosis and osterochondritis dissecans

Answer 7

-osteochondrosis-abnormal growth at end of bone
-osterochondritis dissecans-when a piece of bone and the attached cartilage break down and become loose
-dogs, pigs, horses
-pitted ball joing- femur/humerus
-more males than females
-exacerbated by rapid weight gain and movement

Question 8

hip dysplasia

Answer 8

-shallow acetabulum
-more severe cases show symptoms at younger ages
-occurs in most large dogs and breeds
-inc age=inc arthitis=inc pain
-possible environmental triggers:
-rapid growth (overfeeding?)(now large puppy foods)
-dietary imbalance (excessive Ca intake)
-over-excercise?

Question 9

why a gender incidence difference

Answer 9

-possible sex differential threshold?
-or sexes reach threshold at different times (males grow faster then females but same height of thrshold)

Question 10

epilepsy

Answer 10

-multifactorial sizure disorder (usually-can be causes by a single gene but another kind which is multifactorial)
-more common in certain breeds, such as belg shep
-polygenic trait
-stress and sex hormones (female and neutered dogs more at risk)

Question 11

risk of recurrence

Answer 11

-chance the trait will occur in another offspring

-theoretical risk (for mendelian traits)
-25% recessive
-50% for dominant

-empiric risk (for multifactorial traits)
-observed reoccurrence risk

Question 12

risk of recurrence- multifactorial

Answer 12

-average multifactorial risk
-3-5%
-calculated risk
-=square root of incidences
-ie 1/1000
-3% recurrence risk

-this risk rises exponentially for eveery first degree relative which includes: sibs, parents, offsp
~5% 1 parent or 1 sib or 1 offspring
~10% 1 parent + 1 sib
~20% 1 parent + 2 sibs

Question 13

when does risk of recurrence increase

Answer 13

-more severe the case or the earlier the onset
-mating is consanguineous
-trigger is common
-multiple family members affected

Question 14

what is the burden of the disease

Answer 14

-perception of:
-severity of symptoms
-cost of treatment
-pain or discomfort
-things to consider when looking at multifact and breeding

Question 15

breeding decisions and multifactorial disease

Answer 15

-client must weigh risk and burden
-5% risk of eye cencer… but about 50% of the carcass is then condemned
-5% risk of hip displasia… active dog or st. bernard

Question 16

genetic advice for breeding decisions for multifactorial

Answer 16

-avoid repeat mating that produced multifactorial diseased offspring
-suggest “health lifestyle” changes in breeds know to be susceptible

Question 17

what are some goals of future breeding programs

Answer 17

-fewer antibiotics used, especially in meat production
-greater longevity
-increased quality of life/health
-increased milk production (with peak at 4-5 years of age in dairy cattle)