Genetic disorders provide a unique opportunity …
Decreased or absent expression of gene A which is accompanied by a deficit in function B - role of A in implementing B
Pinker (2001) referred to the 21st century as …
The dawn of cognitive genetics
Phenylketonuria (PKU)
Affects 1 in 10,000 individuals
It is responsible for 1% of all hospitalised cases of learning disabilities
It is caused by a dysfunction in pathway producing the amino acid tyrosine so the body is unable to break down phenylalanine
High levels of this can damage the brain
Sufferers have learning disabilities, behavioural difficulties and epilepsy
Medelian laws apply
Huntington’s disease…
Forgetfulness due to progressive damage of basal ganglia and cortex
Also explained by Mendelian laws
Beyond Mendel…
Abnormalities in chromosomal numbers
Williams syndrome
Deletions due to errors in replication of DNA during gamete formation
Prevalence does not increase with age of parents like Downs
It is caused by a micro deletion of chromosome 7
Some symptoms are facial dysmorphology
IQ average is 50-70
There is a great variability in general performance and cognitive profile, which is caused by a dissociation between language and cognitive ability
Down’s syndrome
This is caused by sporadic changes, a segregation of alleles when gametes are produced. This causes an extra chromosome 21. Can also be called trisomy 21.
Approximately 1 in 10,000
Prevalence increases depending on the age of parents
Some symptoms are facial dysmorphology from birth. Short stature and learning difficulties later on. Average IQ - 55
X linked genes
Females are XX so detecting a gene located on the X chromosome is easier
Colour blindness was the first reported case of human x linkage.
XO - women with Turners syndrome
1 in 2,500 births
Short stature and infertility.
Klinefelter syndrome. Men with X + XY
1 in 750 male births.
Problems due to hormonal imbalances
Causes them to develop female characteristics
Fragile X syndrome - gene dysfunctions for single genes on the X chromosomes
1 in 2,000-4,000 boys.
1 in 6,000 girls
Complex profile of relative cognitive strengths. Autism-like
Enlongated face, large ears, large testes
Social anxiety and stereotypic movements
The human genome project…
Has increased the probability of identifying genetic origins for an increasing number of disorders previously defined just by their symptoms.
