3: Genetics and children Flashcards
How is information stored in genes?
Amino acid sequences
i.e DNA
In which arrangement do DNA strands bind together?
Anti-parallel
What is the sugar forming the backbone of
a) DNA
b) RNA?
a) 2-deoxyribose
b) Ribose
Which bases pair in DNA?
And in RNA?
A-T; C-G
A-U; C-G
DNA strands are bound to which proteins?
Histones
Tons of DNA strands combine to form what?
Chromosome
How many base pairs are there in the human genome?
3 000 000 000
3 billion
How many genes does each human have?
30 000
30 thousand
How many polymorphisms does each person have on average?
3 000 000
3 million
Which genetic testing technique is used to find
a) large changes affecting the entire genome (e.g extra chromosomes)
b) tiny changes affecting one or a few bases (e.g point mutation)?
a) Array genomic hybridisation (aCGH)
b) Next generation sequencing (NGS)
How does aCGH work?
Detects BIGGER changes (e.g big deletions, chromosome duplications)
Compare sample to control DNA and ask “Is there more or less DNA?”
If aCGH finds half as much DNA as the control, a ___ mutation has occurred.
deletion
If aCGH finds 50% more DNA than the control sample, a ___ mutation has occurred.
duplication
aCGH can only detect (balanced / unbalanced) chromosome changes.
unbalanced changes
Which genetic disorder is caused by a deletion in chromosome 22?
Digeorge syndrome
What are the symptoms of Digeorge syndrome?
Developmental delay
Vision / hearing problems
Mouth deformities e.g cleft palate
Congenital heart disease
Hypoparathyroidism causing seizures
Which genetic test is used to identify Digeorge syndrome?
Why?
aCGH
Picks up bigger genome changes (e.g deletions or duplications)
Digeorge syndrome is caused by a deletion in chromosome 22
- The cat sat on the mat
- The cat
- The car sat on the mat
- The cat spa to nth ema t
- The cas ato nt hem at
- The cat on the mat
- The cat cat sat on the mat
Name each type of mutation.
Normal
Stop mutation
Missense mutation
Insertion mutation
Deletion mutation (out of frame >>>>)
Deletion mutation (in frame)
Triplet expansion mutation
When is NGS used?
Small changes to genome
e.g a mutation in one gene
What is an example of a disease which could be identified by NGS?
Kabuki makeup syndrome
wouldn’t worry about remembering it
What does de novo mean?
An acquired mutation
Arising spontaneously in the patient
What is the percentage chance of finding a de novo mutation in a child with a developmental disorder?
> 30%
For children with non-specific developmental disorders, which genetic test should be done first?
NGS
to try and find a small mutation
Although genetic tests are useful in diagnosing disease, what information is essential?
History
Examination
because there are too many genes to analyse
