Lecture 1 Flashcards
Molecular Genetics of neurodevelopmental disorders: Genetic basis & strategies to identify risk factors
What is a genetic disease?
A genetic disease is a disease that is caused by
a change, or mutation, in an
individual’s DNA sequence. A
genetic disorder is an illness
caused by changes in a
person’s DNA.
How is genetic information kept or lost in the population?
Genetic information kept or lost in the population through selective pressure (SP)
What is selective pressure (SP)?
SP incudes factors of influences which may improve/lessen reproduction in a species’ population and therefore contributes to evolutionary change or even extinction through natural selection
What are the different types of selective pressure?
A. stabilizing selection
B. bidirectional selection
C. disruptive selection
What is stabilizing selection?
individuals closest to the mean have highest fitness. Same mean but less variation
What is bidirectional selection?
individuals at one extreme have highest fitness, with an evolutionary trend towards that extreme
What is disruptive selection?
if both individuals at the extremes have high fitness, variation in the population is increased, and a bimodal pattern may result
What is the difference between Mendelian and non-mendelian inheritance for genetic disease?
Mendelian: rare ( 1% > ) –> monogenic/oligogenic
non-Mendelian: common ( 1% < ) –> multifactorial/complex/polygenic
What does oligogenic and polygenic mean?
Oligogenic: few genes
Polygenic: many genes
What is the difference between multifactorial and rare diseases?
In (most) rare diseases
Genetic factors are
the cause for disease!
In Multifactorial diseases
Genetic and environmental factors are
risk factors for disease!
What is Falconer’s Threshold Model (1981)
Falconer’s Threshold Model (1981):
A combination of risk factors (genetic and environmental) above a threshold is necessary for disease manifestation, with a cumulative effect increasing the likelihood of the trait appearing in families.
Individual genetic risk factors have small effects, but the combination of multiple genetic and environmental factors must exceed a threshold for disease manifestation.
What is the relationship between sample size and genetic effect size?
Sample Size & Genetic Effect Size:
Larger sample sizes are needed to detect smaller genetic effect sizes. This is because smaller effects require more statistical power to be reliably identified, while large-effect variants are easier to detect in smaller samples.
What are we looking for when determining heritability?
finding the genes that:
- Increase the risk of the disease
- Explain the physiology of the disease
- Predispose to disease
How is heritability defined?
- Is a proportion, its numerical value will range from 0 (no genes
involved) to 1 (genes explain everything) - Is an abstract concept. No matter what the numbers are, it tell us
nothing about the specific genes that contribute to a trait - Is a population concept. It tells us nothing about an individual
