Lecture 13 - Molecular Aspects of ID Flashcards
Describe DSM diagnostic criteria for ID.
Onset during development (if a child has a head trauma then has LD, considered to have an ID but if the same happens to an adult they are just considered to have head trauma).
Deficits in conceptual, social and practical domains.
Deficits in intellectual functions on clinical assessment and intelligence testing.
Deficits in adaptive functioning.
Describe the link between comorbidities and ID.
Almost all people with ID have a comorbidity.
The lower the IQ the higher the risk of epilepsy so genetics of epilepsy and ID may overlap.
High comorbidity between ID and ASD so genetics relevant.
What are some environmental causes of ID?
Infections
Torch infections during pregnancy
Fetal alcohol disorder.
Describe karyotyping for elucidating genetic architecture of ID.
Staining condensed chromosomes.
Easy and cheap
Resolution is poor, can only see larger things.
Describe FISH for elucidating genetic architecture.
Hybridise a probe known to be attracted to a particular area of genome and then stains it.
Better resolution but not great.
Can see micro deletions and micro duplications.
What is mostly done today to elucidate genetic architecture?
Sequencing, more affordable, best resolution.
What is the most common genetic cause of ID?
Down syndrome.
If you look at people with down syndrome IQ, there is still a normally distributed curve, it is just lower on average compared to the general pop.
What is Klinefelter syndrome?
2x and 1y chromosome - not associated with ID but some people with ID have this disorder.
What is fragile X syndrome?
Most common inherited cause of ID.
When a parent passes down the mutation, it grows so becomes more severe down generations.
Trinucelotide repeat expansion, CGG repeated over and over. If you have more than 200 of these repeats you have it.
How many ID genes are there to date?
1000, everywhere apart from the Y chromosome.
Describe Rett syndrome.
X-linked ID.
MECP2 occurs 1 in 10000.
Almost all people with this have autism and ID.
How many robust autism genes are there and how many possible autism genes are there?
120 robust
400-500 possible
Why should we term the genes involved with autism and ID brain development genes?
Pleiotropy between these genes so they can cause several different disorders not just autism/ID.
The genotype does not predict the phenotype as well.
What is are some of the more common genetic causes of ASD?
16p11.2
15q13.3
