Transition block: genetics Flashcards
What is the first step in the ‘Central Dogma’ of
making a protein from a gene ?
transcription
There is a single base mutation of a ‘C’ to a ‘T’ in the 3rd
exon of the ASXL3 gene.
What is the most likely reason that this has no effect
on protein sequence ?
Codon usage shows redundancy
A 64 year old man is affected with hypertrophic cardiomyopathy and has a Ile345X (stop) mutation in the MYBPC3 gene. His 32 year old son is healthy and has a normal heart scan, but is shown to carry the same mutation.
What is the most likely genetic explanation for the normal scan in his son ?
The mutation has variable penetrance
Next generation sequencing of genes has an advantage over Sanger (conventional) sequencing because
It allows sequencing of a much larger number of
genes
Array Comparative Genomic Hybridisation (aCGH) is
preferable to karyotyping as a first test for chromosome
analysis because
It has higher resolution
A 10 year old girl has severe learning difficulties. A
mutation Arg126Try (Arginine to tryptophan) is
identified in the gene that causes Bainbridge Roper
Syndrome (ASXL3).
Which would be the strongest piece of evidence that
this genetic variant is causing the learning difficulties ?
It is present in the child but not both normal parents
A 12 year old girl has severe learning difficulties. A
deletion of a single base is identified in the 3rd exon of
the DEAF1 gene (A gene that causes learning
difficulties). This is not found in either parent.
How would you classify this genetic variant ?
Definitely pathogenic
A 20 year old man has Neurofibromatosis type 1 (NF1).
A base change altering an amino acid (Arginine to
Histidine) in the NF1 gene is identified. It is also seen in
5% of the general population.
How would you classify this genetic variant ?
Definitely benign
What characteristic of a cancer cell is central to
allowing it to acquire further new characteristics ?
Genomic instability
A 32 year old woman wishes to be tested for
Huntington Disease. This is an untreatable autosomal
dominant condition that affected her father.
Which ethical principle is most important in genetic
counselling for your patient when she asks for a genetic
test ?
Patient autonomy
How is cystic fibrosis inherited?
autosomal recessive
What is the likelihood of being a carrier for CF?
1/25
What is redundancy?
when a different codon sequence produces the same amino acid
What is detected by aCGH?
unbalanced chromosome translocations
Which genetic test can be used to detect a point mutation?
PCR
