Chromosome techniques Flashcards
Light regions on G-banding are predominantly which bases?
G-C
Dark regions on G-banding are predominantly which bases?
A-T
What does denaturation do to DNA?
Makes it single stranded
How long and at what temp is hybridisation (in FISH) ?
Overnight at 37c
What are centromeric DNA probes used for most?
Trisomy disorders, bone marrow transplant success! (different sexes)
What are some of the consequences of copy variations?
Susceptibility or resistance to disease and cancers, for example CCL3L1 resits HIV and FCGR3B predisposes inflammatory and autoimmune
What does MLPA stand for (genetics) ?
Multiplex Ligation-dependent Probe Amplification
What is replacing karyotyping as a first line test?
Microarray CGH
A high degree of fluorescence of control DNA on a microarray chip is significant of what?
Deletion
At least how many oligonucleotides are needed to be next to each other to investigate?
3
What size fragment is looked at with copy number change?
> 150K
Referalls for Arrays usually involve people presenting with which types of problems?
Learning disorders and Dysmorphic features
Advantages of Arrays?
Early diagnosis
High resolution
Greater accuracy
Relevant gene info
Disadvantages of arrays?
Low levels of mosaic not detected
Only dosage changes measured
Good DNA needed
Benign things found
Chromosome paint in FISH can show what?
Translocation
What do you do with blood for G-banding?
You need 2-5ml unclotted
Stimulate T-lymphocytes
Incubate 3 days
If a parent carries a robertsonian translocation between 21-22 what is the recurrence risk in future pregnancy?
100%
Why do male carriers have less chance of fertilising?
The sperm is less viable
What does a haplosufficiency score indicate?
Low scored indicate high chance of pathogenecity
How many recurrent miscarriages may prompt genetics screening?
3
Those who may be infertile due to chromosome changes… which?
47XXY or 45X
What weeks is amniocentesis performed?
16
Chorionic villus sampling and non invasive testing occurs at what week?
12
How does NIPT work?
Free DNA from foetus assessing aneuploidy
What was the serum screen known as? includes what? (risk)
Triple test,
alpha FP - -
oestriol - -
HcG ++
Cancer acquired chromosomal changes are usually what type?
Translocations
Chronic myeloid leukaemia is associated with which chromosomal abnormality?
Philadelphia t(9;22)
bcr/abl gene abnormal protein
MYCN gene is associated with which tumour?
Neuroblastoma
Front line cytogenetic test should be?
Array CGH
Which is more targeted? FISH, G-banding or array?
FISH
What is Quantitative fluorescent PCR mostly used for?
Amplifying short tandem repeats
What is quantitative fluorescent pcr used for mostly?
Aneuploidy in newborns, or prenatal dosage changes
