Complex Inheritance Flashcards
Most of the human traits are: (4 descriptions in genetics)
Polygenic, Continuous, Additive effects and Multifactorial
What does Polygenic means?
Polygenic- caused by many genes
What does Continuous (in genetics..) means?
Continuous- quantitative traits
What does Additive effects means?
not dominant or recessive
What does Multifactorial means?
Multifactorial - environmental factors also involve
Examples for Complex inheritances traits:
Examples for Complex inheritances traits:
Skin color, weight, height, glucose in blood, cholesterol in blood, BP, shoe size, IQ etc.
Characteristics of multifactorial traits (diseases):
What kind of Pattern - Mendelian or not?
Characteristics of multifactorial traits (diseases):
No Mendelian pattern of inheritance
Characteristics of multifactorial traits (diseases):
What increases risk of diseases - Many or Few Children?
Characteristics of multifactorial traits (diseases):
Recurrence risk increases with the number of affected children in a family (because same lifestyle)
Characteristics of multifactorial traits (diseases):
What increases risk of diseases - Relative that is severely or moderately affected?
Characteristics of multifactorial traits (diseases):
There is a higher recurrence risk if the relative is more severely affected
Characteristics of multifactorial traits (diseases):
What increases risk of diseases - Insest or Normal realtionship?
Characteristics of multifactorial traits (diseases):
Marriage of relative moderately increases the risk (not significant risk)
Characteristics of multifactorial traits (diseases):
Does the disease affect both/one/one more than other gender?
Characteristics of multifactorial traits (diseases):
Disease occurs more frequently in one gender, but is not sex-linked / -limited (one more than other)
Characteristics of multifactorial traits (diseases):
Concordance rate in monozygotic and dizygotic twins contradicts or falls in line with Mendelian proportions
Characteristics of multifactorial traits (diseases):
Concordance rate in monozygotic and dizygotic twins CONTRADICTS Mendelian proportions
Characteristics of multifactorial traits (diseases):
Does environmental factors - (+)/(-)/both/none influence the disease?
Characteristics of multifactorial traits (diseases):
Environmental influence can increase or decrease the risk of the disease
Characteristics of multifactorial traits (diseases):
Do the diseases occurs frequently in ethnic groups or is it worldwide?
Characteristics of multifactorial traits (diseases):
The disease occurs more frequently in a specific ethnic group
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
Familial aggregation
Familial aggregation:
Frequency of the disease in relative / siblings compared to frequency in population
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
λs =
λs =Frequency of the disease in relative / siblings compared to frequency in population
(Familial aggregation)
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
λs > 1
What does that mean?
λs > 1
High genetic influence
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
λs < 1
What does that mean?
λs < 1
Low genetic influence
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
Twin studies - What is Concordance?
Twin studies - Concordance:
both of the twins have the trait
Methods applied in complex inheritance- used in identification of genetic (environmental) background:
Twin studies - What is Discordance?
Twin studies - Discordance
only one of the twins have the trait
Factors which make the determination of genetic background of the complex disease difficult: (4)
- Genetic heterogeneity (locus or allelic)
- Phenocopy
- Pleiotropy
- Incomplete penetrance
What is a Haplotype?
Haplotype:
a set of genetic determinants located on a single chromosome.
What is Linkage disequilibrium (LD)?
Linkage disequilibrium (LD): the non-random association of alleles at two or more loci that may or may not be on the same chromosome.
What is Linkage disequilibrium (LD) used for?
It is used in population genetics for the calculation of the chance of co-inheritance of two alleles.
In other words- it is the occurrence of some combinations of alleles in a population more or less often than would be expected from a random formation of haplotypes from alleles based on their frequencies.
