G4- Genetic diseases Flashcards
what is the human genome project?
- The blueprint for the human body and all it’s biological, biochemical and psychological functions
- The sequence of the chemical bases (A, T, C and G) in the DNA on the 24 different human chromosomes
what are Qualitative traits?
ABO blood antigens
what are quantitative traits?
height, weight or tooth size
Describe the modes of inheritance.
- Paired chromosomes (22) plus sex chromosomes
- Gene pairs at same locus (alleles)
Describe autosomal dominant.
-When disease mutations are passed down , anyone who inherits these gene will be affected
-Disease seen in all generations
-50% risk of affected child if parent is affected
-Disease severity can be variable
(individuals with a mutation may not show disease) Males and females equally likely to be affected
what is crouton syndrome?
skull bones fuse prematurely and restrict brain
what is Van Der wood syndrome?
- cleft lip or palate
- lower lip pits
what is penetrance?
probability that presence of disease genotype will cause disease
what is expressivity?
Variation in the severity of expression of a particular gene
Describe autosomal recessive.
- if one copy is transmitted- it will not tramit the disease iself,
- it needs two faulty copies of gene to cause disease
- Often only one generation affected
- 1 in 4 risk of an affected child if parents carriers
- Increased likelihood in consanguineous families
what increases risk of recessive conditions?
consanguinity (incest)- same gene pool so increases risk
Name an example of a recessive condition.
cystic fibrosis
Describe X linked recessive inheritance.
-Gene fault lies on the X chromosome
-A female carries a mutation but will not show major features of disease
• For a female carrier
– Half of the male children of a carrier will be affected – Half of the female children will be carriers
• If an affected male has children
– All of male children will be normal (no male to male transmission)
– All of female children will be carriers
describe X inactivation.
In Female Cells only One X chromosome is active
Describe X-linked phenotype.
-Heterozygous female may show features of the condition
• X-chromosome with mutant allele remains active in some cells (disease)
• In those with normal allele - no disease manifestation
Describe multifactoral disorders.
-Spectrum of genetic disease
• Relative genetic and environmental contribution
• Multifactorial threshold model
Is there any association between socio-economic status and prevalence of disease?
in deprived areas there is more environmental factors: smoking, drinking , illness that increase risk of disease
what is a way of preventing disease?
dietary supplementation
Describe pharmacogenetics.
-Individual variation in the capacity to metabolise and use effectively particular compounds
• Characterisation of patients before therapy - improved response rate
• Targeted therapy - improved cost- effectiveness
