Introduction Flashcards
Polygenic
Influence of many genes
Penetrance
Proportion of those carrying disease-causing mutation that express traits
What is complete penetrance?
100% of those with mutation will develop disease
What is example of disease with complete penetrance?
Neurofibromatosis type 1
What is low penetrance?
Will only sometimes produce trait - can be difficult to distinguish environmental from genetic factors
Multifactorial
Environmental and genetics
One organ system affected
Mendelian
Mutations in single genes (monogenic disorders)
Chromosomal
Often occur spontaneously (deletions, trisomies, duplications), causing huge groups of genes to be changed
Multiple organ systems affected at multiple stages in gestation
What is Trisomy 21 and what is it an example of?
Chromosomal disorder - Down syndrome
Failure of 21st chromosome to separate, producing an extra copy (cell has 24 chromosomes)
Where does mitochondrial inheritance come from?
Mutation resides on mitochondrial DNA
Where does mitochondrial genome come from?
Oocyte –> always maternally inherited
Which tissues are most affected by mitochondrial diseases?
Tissues that require lots of energy
What is multifactorial inheritance controlled by?
Many genes with small additive effects (polygenic) plus effects of environment
Effect of each gene is small
What does multifactorial normally affect?
One organ system
