Multifactorial Inheritence

Question 1

Polygenic traits:

Answer 1

Variation thought to be caused by a combined effect of multiple genes but no environmental factors

Question 2

A disease with multiple occurrences in the family but no clear pattern of Mendelian inheritance is indicative of:

Answer 2

Multifactorial traits/diseases

Question 3

Traits that occur more frequently in a specific ethnic group are indicative of

Answer 3

Multifactorial traits

Question 4

In the polygenic model, the ________ genes controlling the trait, the ________ possibilities for what the trait can look like

Answer 4

More, more

Question 5

Human height is considered a _______ trait

Answer 5

Polygenic

Question 6

The threshold model can only be applied to ________ traits

Answer 6

All or nothing quantitative

Question 7

Liability refers to

Answer 7

Genetic and environmental factors that influence development of disease

Question 8

In the threshold model, the value of the threshold can only change

Answer 8

Between populations, not within a population

Question 9

Major factors affecting recurrence risk

Answer 9

Number of family members affected, degree of relationship, sex of proband, severity of proband

Question 10

What is needed to distinguish between multifactorial inheritance versus single-gene inheritance with reduced penetrance or variable expressively?

Answer 10

Large data sets of families

Question 11

Dizygotic =

Answer 11

Non-identical twins (two embryos)

Question 12

Monozygotic =

Answer 12

Identical twins

Question 13

Concordance

Answer 13

Both twins share a trait

Question 14

Discordance

Answer 14

Both twins do not share a trait

Question 15

Heritability definition

Answer 15

Proportion of the variation that can be attributed to genes

Question 16

The closer to 1 the calculated heritability, the _________ the genetic influence

Answer 16

Greater

Question 17

Heritability equation

Answer 17

H = 2(Cmz - Cdz)

Question 18

Twin study limitations:

Answer 18

1. Uterine environment (shared or unshared placenta
2. Somatic/de novo mutations
3. Underestimation of environmental contribution (environment also identical)

Question 19

If calculated hereditary is greater than one, what mistake was made?

Answer 19

“Overestimation” of genetic factors because of shared environmental factors

Question 20

Adoption study limitations

Answer 20

1. Prenatal environment can look like genetic factors
2. Time spent with biological parents
3. Adopted by relatives
4. Health data of birth parents unavailable

Question 21

An adoption or twin study can only be used as a ________ of how environment and genetics influence a disease

Answer 21

Preliminary indication

Question 22

Pyloric stenosis:

Answer 22

Hyperplasia of muscles at pylorus of stomach causing obstruction of gastric emptying

Question 23

Symptoms of pyloric stenosis

Answer 23

Recurrent vomiting, dehydration, electrolyte imbalance

Question 24

For pyloric stenosis, the threshold is _______ in males

Answer 24

Lower

Question 25

Pyloric stenosis is considered a ______ disease

Answer 25

Multifactorial

Question 26

Schizophrenia is considered a _________ disease

Answer 26

Multifactorial

Question 27

Common congenital multifactorial diseases

Answer 27

1. Cleft lip/palata 2. Pyloric stenosis 3. Club foot 4. spina bifida

Question 28

Common adult multifactorial diseases

Answer 28

1. Coronary artery disease 2. Obesity 3. Alcoholism 4, cancer 5. Diabetes 6. Schizophrenia

Question 29

The polygenic model produces a ______ distribution

Answer 29

Bell-shaped curve

Question 30

In the polygenic model, many genes contribute to one trait, and each individual gene:

Answer 30

Follows Mendelian inheritance

Question 31

True or false: the threshold model fits with all human multifactorial diseases

Answer 31

False, diabetes type 2 does not fit well

Question 32

Bob was the first child in his family with pyloric stenosis. Martha was the first child in her family with pyloric stenosis. Which family has a higher recurrence risk?

Answer 32

Martha’s family, males have a lower threshold for pyloric stenosis, therefore Martha had more liabilities

Question 33

Recurrence risk ________ if the proband is of the less commonly affected sex

Answer 33

Increases

Question 34

Example of a genetic disease with both a single gene and multifactorial cause

Answer 34

Obesity caused by a deficiency of leptin leading to hyperplasia (gene) obesity is also multifactorial

Question 35

Example of a multifactorial disease with a strong environmental contribution

Answer 35

Lung cancer - smoking

Question 36

Example of multifactorial disease with a strong genetic contribution

Answer 36

Breast cancer- BRCA genes

Question 37

Heritability only applies to

Answer 37

A certain population in a given environment. It is not universal

Question 38

Disorders with multifactorial inheritance will be the cause of morbidity and premature mortality in nearly _________ of individuals in their lifetime

Answer 38

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