Lecture 4 GiM Flashcards
What is mendelian inheritance?
Pattern of inheritance that obeys Mendel’s laws of segregation – dominant, recessive, X-linked
What is complex pattern of inheritance?
It tends to be used vaguely to describe something with an inherited but non-Mendelian component
What is polygenic inheritance?
The result of the action of multiple genes
What is multifactorial inheritance?
The result of multiple factors, usually including both genetic and environmental factors
What is familial clustering?
Relative risk to the second sibling ( Basically, just divide risk to second sibling/ general population)
What is the finding of twin studies?
Genetic characters should have a higher concordance in monozygotic (MZ) twins compared to dizygotic (DZ) twins…
What is the problem with twin studies?
assumption that the degree of environmental sharing is the same for MZ twins
and
DZ twins can share more than half their genes
What are the 5 characteristics of Polygenic/Complex/Multifactorial inheritance?
- Phenotypes determined by action of many genes at different loci
- Genes are not dominant or recessive but additive
- Includes many human traits/common diseases; blood pressure, head circumference, height, intelligence
traits tend to be normally-distributed in the general population ie forms a Gaussian “bell-shaped curve” with even distribution about a mean - Diseases tend to run in families but not in a “simple” Mendelian fashion
- Usually influenced by environment as well
What is additive genes?
Additive genes are those genes that code for the same trait and their effects work together on the phenotype.
(An example of a function of additive genes is on the eye colour. Several genes work together to determine the colour of the eye of an offspring)
What is the function of genetic association studies?
Seek to relate variation in human DNA sequence with a disease or trait
Association method provides greater power to detect common genetic variants conferring susceptibility to complex phenotypes
In what types of condition does linkage analysis is used?
The condition in which it is rare in population but has a great effect size. (Rare alleles causing Mendelian diseases)
What is linkage disequilibrium?
A state involving two loci in which the probability of a joint gamete is not equal to the product of the probabilities of the constituent genes. The difference between these quantities is the increase of the disequilibrium; there are many causes of the disequilibrium.
Most disease bearing chromosomes in population are descended from one (or a few) ancestral chromosomes
What are the drawbacks of population association study based on linkage disequilibrium?
Careful selection of the control group is essential, large numbers of cases are needed and association may depend on the population history
What is thrifty phenotype hypothesis?
The thrifty phenotype hypothesis proposes that the epidemiological associations between poor fetal and infant growth and the subsequent development of type 2 diabetes and the metabolic syndrome result from the effects of poor nutrition in early life, which produces permanent changes in glucose-insulin metabolism. These changes include reduced capacity for insulin secretion and insulin resistance which, combined with effects of obesity, ageing and physical inactivity, are the most important factors in determining type 2 diabetes
What is the advantage of population association study?
Population association study can detect association to
