complex inheritance

Question 1

qualitative dichrotomous traits

Answer 1

traits that are either present or absent and follow a Mendelian pattern of inheritance

Question 2

complex, multi factorial traits

Answer 2

can be continuous or or dichotomous

continuous multifactorial traits are traits like height and blood pressure

examples of dichotomous traits are type 2 diabetes and cardiovascular disease

Question 3

Describe the bell curve of multifactorial diseases and relate it to varience and how risk for multifactorial disease is calculated

Answer 3

the risk of acquiring a multifactorial disease that is caused by multiple genetic mutations and environmental factors is plotted on a bell curve

those with a high degree of succeptability have a greater then average chance of acquiring a multifactorial disease based on genetic predisposition and environemtnal exposure

variance = standard deviation²

^{varience described the extent to which people with a trait vary}

Question 4

Describe heritiability.

What does a h² of 0 indicate

What does a h² of 1 indicate

What does a h² between 0 and 1 indicate

Answer 4

h²= (V of DZ pairs - V of MZ pairs)/(V in DZ pairs)

• heritability measures the extent to which a trait is caused by genetic factors or envrironmental factors
  
  • h² of 0 indicate trait caused by environment
  • h² of 1 indicates trait caused by genetics
  • h² between 0 and 1 indicates trait caused by genetics and environment

Question 5

What is an example of a multifactorial disease caused by **the additive effect of gene loci **

(think mel)

Answer 5

Retinis pigmintosa is caused by the additive effect

• both Periperin and ROM1 must be present to cross the threshold for photoreceptor death and loss of vision

Question 6

Hirshsprung Disease

Answer 6

a loss of ganglion cells of the colon that control peristalisis

(contractions that move food through the colon)

• Affects males to females 2:1
• medelian forms are assoicated with complete loss of function of the RET gene
  
  • disease can also be caused by multiple mutations of RET gene and associated alleles, this results in mutlifactorial inheritance

Question 7

Type 1 diabetes

Answer 7

Autoimmune diseases with genetic link attributed to MHC receptor mutations

• multifactorial inheritance, genetic mutations increase risk but there is also an environemntal association

Question 8

Idiopathic cerebral vein thrombosis

Answer 8

mutifactorial and additive inheritance

Clots form in brain without trauma in young adults

factor V and prothrombin mutations + environmental factor (use of oral contraceptives) increases the likelihood of clots when mutants are present

Question 9

Alzheimer’s

Answer 9

o Alzheimer’s

• Late onset of alzheimers
  
  • multiple copies of apoE alleles predict Alzheimer and other mutations + environemntal factors lead to Alzheimers
• early onset alzhemers
  
  • mendalian form of the disease with strong genetic association (rare)

Question 10

mutlifactorial congeital malformaitons

(cleft lip, spinal bifida, neural ftube defects)

Answer 10

mutlifactorial with genetic link + environmental factors

• folic acid supmlements during pregnacy reduce the risk of these malformaitons significantly

Question 11

bipolar and schizophrenia

Answer 11

There are both genetic and environemtnal facotors that lead to the development of bipolar and schizophrenia.

• family history of either disease increases the risk of getting it

Question 12

A new disease has a relative risk ratio less then 1

Is this disease caused by complex inheritance?

Answer 12

No.

relative risk ratio λr - a quantitative measure of the degree of familial aggregation of a disease

• Values of λr >> 1 suggests complex gene mechanism contribute to the disease