Cytogenetics And Molecular Genetics Flashcards
Explain G banding of chromosomes
Dark G bands show heterochromatin- condensed chromatin gene poor
Trypsin can’t degrade chromatin = dark band
Light G bands- euchromatin is uncondensed = trypsin acceded chromatin degrading it = g band light
What 2 types of satellite / repeat dna are there
Alpha satellite - centromere repeat
Beta satellite - VNTRs , micro satellites, minisatellites
Explain the difference between cytogenetics and molecular genetics
Cytogenetic is whole genome analysis (shows all chromosomes)
Lower base pair resolution
Looks for issues like trisomy in the karyotype
Molecules genetics-
Specific chromosome analysis
Higher 1 Base pair resolution
Uses PCR to amplify small dna parts to analyse base pairs for genetic diseases eg snp analysis
When do we analyse chromosomes
During cell division when they uncondense
What are the cytogenetic steps of preparing cell culture
They stimulate cell division in the culture
Freeze it in metaphase stage (harvesting)
Banding stain is added
Analysis begins
What does constitutional cytogenetics mean
Diseases analysed other than cancers
What 3 analyses use cytogenetics
Prenatal cytogenetic analysis
Postnatal cytogenetic analysis
SNP array- taken for better resolution
Which 3 techniques are used to study small deletions or abnormalities (molecular)
Fish , QF PCR , snp arrays
How are cells taken for analysis in prenatal cytogenetics
Via amniotic fluid or placental tissue
Which chromosomes are seen using molecular genetics
Chromosome 13,18 and 21
Why are chromosomes 13,18 and 21 analysed
Detect Patau trisomy 13
Edward 18 trisomy
Down 21 trisomy
How does QF PCR work to detect abnormalities
Amplification of chromosomes 13,18 and 21 taken
Using primers which flank repeat positions
Quantifies how much dna there is present
If abnormal eg deletions or insertions more testing done
What happens if QF PCR is found to be abnormal amounts of dna
Whole genome analysis is done looking at karyotype and this shows things like trisomy etc
What kind of chromosome rearrangements can cause trisomy
Robertsonian translocation (fusion of chromosomes)
How is postnatal analysis done
QF PCR is done and if abnormal the genome analysis is done
If normal however snp array is done for better resolution incase
How do SNPs arrays work
Analyse SNPs of whole genome on wells
How are SNPs analysed in the wells of the snp array
Using bead chip techniques
Dna is hybridised with primers with beads attached which stop 1 nucleotide before snp
This then is extending by a labelled nucleotide and this identified the snp base added
How can snp arrays show deletions or duplications (inherited due to unequal sister chromatid exchange)
If more or less SNPs are seen through labelled bases
Why are deletions picked up better than duplications/trisomy
People are likely fine if they have duplications but can die if they have deletions
What happens due to unequal crossing over
Disorders
More or less SNPs on the dna
How does fish analysis work
A single DNA sequence called a probe is labelled and annealed with complementary target dna via base pairs
This can detect abnormalities due to deletions or duplications due to the fluorescent probs
What is next gen sequencing
Where dna is broken down and has adaptors on the ends
It’s amplified using PCR
The dna library is attached to a flow cells which has oligonucleotides on it
Dna fragments attach to complementary nucleotides on flow cell
The sticky ends of dna fragments then attach to fluorescent nucleotides added
Can compare the sequence to a reference to detect abnormalities
What does cancer cytogenetics aim to do
Diagnose, show prognosis and treatment available for the patient
What kind of sample is taken for cancer cytogenetics
Sample from skin or bone marrow or blood
Give an example of where dna analysis of someone with lymphoblastic leukaemia helped prognosis and treatment
Because if they find hyper diploidy
They have good prognosis and therefore done need treatment unlike people without hyper diploidy
Which drug was discovered due to the clear analysis of chronic myeloid leukaemia inversions showing bad prognosis
Imatinib
