Genetic Disorders (chromosomal/DNA mutations) Flashcards
What is a copy number variation in a chromosome?
is duplication or deletion of a considerable amount of DNA (E.g. a gene) meaning there is variation in the chromosome that then goes onto meiosis. e.g. CAG repeat in Huntington’s.
If a woman was having repeated miscarriages, what kind of translocations (balanced/unbalanced) would you expect to see for her and the foetus?
Balanced or normal - for her as unaffected
Unbalanced for foetus as this has more risk
What is the difference between trisomy/triploidy? Are they compatible with life?
Trisomy is 3 of one chromosome e.g. 21 - yes Downs Syndrome. Triploidy is 3 copies of every chromosome not compatible with life. 15% of all miscarriages are this, and term babies die shortly after birth.
Would you use aCGH in a neonate with a heart abnormality and why?
Yes as copy number variations are one reason for congenital cardiac problems - so look for unbalanced translocations.
Would you use aCGH in a child with developmental delays/autism and why?
Yes because learning difficulties/developmental delay can be caused by unbalanced translocations.
Would you use aCGH in recurrent miscarriages and why? What would you use instead?
No you don’t use it pre-term and mother will be either balanced or normal so won’t be detected. Use FISH on mother - can see balanced and unbalanced - for known aneuploidies - need to know what you’re looking for as probe specific.
Would you use aCGH for sperm and egg donors and why?
Yes to check if there are unbalanced translocations that would not be compatible with life. Also some translocations (e.g. Roberstonian) can cause aneuploidies (trisomies etc) that may not be compatible with life.
If you have an ‘apparently balanced’ de Novo translocation in a developmentally delayed child would you use aCGH and why?
Yes because its de Novo it may not actually be balanced. You can use aCGH to see if it is unbalanced.
What is a substitution that results in purine to purine swap or pyrimidine to pyrimidine swap?
Transition
What is a substitution that results in a change from purine to pyrimidine or pyrimidine to purine?
Transversion
Mutation that results in a change in gene product is called ________
Missense
A mutation that results in the change of polypeptide length could be two things what are they?
Stop codon (nonsense), frameshift resulting in early/late stop codon.
What is a mutation called when it doesn’t have an effect on protein?
Silent
What are transposable elements and give 3 consequences of TEs on genes
Jumping genes - specific DNA sequences that have no fixed abode on chromosomes but jump around randomly.
1) Can jump to non coding region - nothing
2) Can jump into gene (more likely if bigger) and inactivate
3) Can jump onto promotor sequence and activate transcription.
Inversions of chromosomes can occur after what DNA damage repair defect?
Error in NHEJ
Error in splicing due to mutations in introns can lead to what in terms of protein made? How?
Change length of protein (as introns left in)
Change amount of protein (as change mRNA - may become non function and degrades)
Would there be an effect if a whole codon is deleted from DNA? is this a frameshift?
No not frameshift as triplet code deleted - this may or may not have an effect on protein.
Give an example of how can insertion occur (what can be inserted)?
Transposable elements
