Week 1 - G - Genetic paediatrics Flashcards
What type of molecule is double stranded and binds in an anti-parallel fashion?
DNA structure
What is the backbone of DNA and what are the bases?
How does it differ from RNA?
DNA is made from a deoxyribose sugar backbone
Adenine, guanine, cytosine, thymine are the bases
RNA is single stranded
Has adenine, guanine, cytosine and uracil
Ribose sugars in RNA
What is the detection method for measuring chromosomal imbalance in a person? (duplication or detection)
Can this method be used for chromosmal translocation?
Use Array Comparative Genomic Hybridisation (Array-CGH)
Can only be used where this an imbalance therefore a translocation will not show
How does Array Comparative genomic hybridisation work?
This test allows identification of a patients genome with a deleted or duplicated chromosomes by comparison with a control sample
If more patient DNA than control DNA hybridises to the dot, it suggests that the region is duplicated in a patient.
If less patient DNA hybridises than control DNA, then the region is deleted in the patient.
Define the difference between mutation and polymorphism?
A mutation is defined as any change in a DNA sequence away from normal.
In contrast, a polymporphism is a change in the DNA sequence that is common in the population (does not express an abnormal phenotype)
What is it known as when the mutation in a child is not present in any other family members?
De-novo mutation
What is the most common start codon?
WHat does this code for?
Most common is AUG
Codes for methionine
What are the three stop codons?
UAA
UAG
UGA
What is a missense mutation?
A point mutation in which a single nucleotide is substituted for another
Name a disease that is caused by triplet expansions?
Instead of having a few CGG, has many
Fragile X syndrome
What gene is mutated due to the triplet expansion in fragile X syndrome?
What is this gene required for?
The FMR1 (Fragile X mental retardation 1) gene is mutated due to the repeat of the triplet CGG
This gene is required for the expression of the FMRP (Fragile X Mental retardation protein) which is required for normal neural development
How does fragile X syndrome present?
Intellectual disability
Obesity
Macroorchidism in males postpuberty
Distinctive facial features
What is williams syndrome? (chromosome and the facial appearance)
Neurodevelopmental condition due to a deletion on chromosome 7
characterised by an elfin facial appearance
Why is William’s syndrome described as the opposite to Autism in terms of its presentation?
Williams syndrome patients are highly sociable and engaging whereas
Autism involves fundamental impairments in social reciprocity and communication
What is used to diagnose William’s syndrome?
FISH (Flouresence in-situ hybridisation)
or
Array-CGH
