Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
Chapter 24: Medical genetics
1
, Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
- personalized medicine = the use of information about a patient’s genotype and other
clinical data in order to select a medication, therapy or preventative measure that is
specifically suited to that patient
- many genetic diseases are the direct result of a mutation in one gene
- some are due to a combination of mutated alleles, usually not due to loss-of-function
alleles
24.1: inheritance patterns of genetic diseases
A genetic base for a human disease may be suggested by a variety of observations
- several observations are consistent with the idea that a disease is caused, at least in
part, by the inheritance of mutant genes
o an individual who exhibits the disease is more likely to have genetic relatives with
the disorder than is someone in the general population
o identical twins share the disease more often than non-identical twins
monozygotic twins genetically identical
dizygotic (fraternal) twins formed from separate cells
geneticists evaluate a disorder’s concordance, the degree to which it is
inherited, by calculating the percentage of twin pairs in which both twins
exhibit the disorder relative to pairs where only one twin shows the
disorder
o the disease does not spread to individuals sharing similar environmental
situations
o different populations tend to have different frequencies of the disease
o the disease tends to develop at a characteristic age age of onset
o the human disorder may resemble a disorder that is already known to have a
genetic basis in an animal
o a correlation is observed between a disease and a mutant human gene or a
chromosomal alteration
Simple Mendelian inheritance patterns of human diseases may be determined via pedigree
analysis
- Autosomal recessive inheritance
o Tay-Sachs disorder
o Frequency an affected offspring will have two unaffected parents
o When two unaffected heterozygotes have children, the percentage of affected
children is 25%
o Two affected individuals will have 100% affected children
o The trait occurs with the same frequency in both sexes
o Can skip generations
o Often caused by mutations that result in a loss of function in the encoded enzyme
- Autosomal dominant inheritance
o Huntington Disease
o Affected offspring usually has one or two affected parents, not the case =
germline mutation
o Affected individual with one affected parent is expected to produce 50% affected
offspring
o Two affected heterozygous have 25% unaffected offspring
o Same frequency in both sexes
2
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
Chapter 24: Medical genetics
1
, Genetics summary – VU BMS 2020/2021
Simone Zweers
Reference: Brooker, Genetics: Analysis and prinicples, 7th edition
- personalized medicine = the use of information about a patient’s genotype and other
clinical data in order to select a medication, therapy or preventative measure that is
specifically suited to that patient
- many genetic diseases are the direct result of a mutation in one gene
- some are due to a combination of mutated alleles, usually not due to loss-of-function
alleles
24.1: inheritance patterns of genetic diseases
A genetic base for a human disease may be suggested by a variety of observations
- several observations are consistent with the idea that a disease is caused, at least in
part, by the inheritance of mutant genes
o an individual who exhibits the disease is more likely to have genetic relatives with
the disorder than is someone in the general population
o identical twins share the disease more often than non-identical twins
monozygotic twins genetically identical
dizygotic (fraternal) twins formed from separate cells
geneticists evaluate a disorder’s concordance, the degree to which it is
inherited, by calculating the percentage of twin pairs in which both twins
exhibit the disorder relative to pairs where only one twin shows the
disorder
o the disease does not spread to individuals sharing similar environmental
situations
o different populations tend to have different frequencies of the disease
o the disease tends to develop at a characteristic age age of onset
o the human disorder may resemble a disorder that is already known to have a
genetic basis in an animal
o a correlation is observed between a disease and a mutant human gene or a
chromosomal alteration
Simple Mendelian inheritance patterns of human diseases may be determined via pedigree
analysis
- Autosomal recessive inheritance
o Tay-Sachs disorder
o Frequency an affected offspring will have two unaffected parents
o When two unaffected heterozygotes have children, the percentage of affected
children is 25%
o Two affected individuals will have 100% affected children
o The trait occurs with the same frequency in both sexes
o Can skip generations
o Often caused by mutations that result in a loss of function in the encoded enzyme
- Autosomal dominant inheritance
o Huntington Disease
o Affected offspring usually has one or two affected parents, not the case =
germline mutation
o Affected individual with one affected parent is expected to produce 50% affected
offspring
o Two affected heterozygous have 25% unaffected offspring
o Same frequency in both sexes
2
