Chromosomal Mutations Flashcards
What is DNA chip technology
A method used to see the expression of genes within the DNA
What are the steps of DNA chip
1) would have the dna, know that each compartment would have the dna with a KNOW sequence
2) would take mRNAs that would normally come from the muscle cells and use reverse transcriptase to create the cDNAs
3) the cDNAs would have the fluorescents attached to them and would allow the microarray tray to be highlighted
4) allow the hybridisation
5) when the complementary mRNAs would attach to the DNA that has been expressed would show a light, the others would not and would be washed away
What is FISH
Fluorescent in-situ hybridisation
This would be used to show the abnormalities in the chromosomes
This would show the translocation, the copy number and the origin material of the chromosomes and the loss of sequence
How would you do FISH
Would have the chromosome in there metaphase form, as this is when the chromosomes would be the most condensed
Would denature the probe and the specimen, to break them open
Would then hybridise them
Would then allow the chromosomes to be seen (normally under uv light)
What mosacism
This is when there would be two different types of cells.
Some of the cells would be normal and some of the cells would have the mutations
The fewer cells with the mutation, the more ‘normal’ the individual will be
What is Robersonian translocation
Where would have the breaking off of two different Acrocentric chromosomes
Would be an issue when the carrier would wish to have kids
What causes trisomy in robersonian translocation
When the carrier (father for example) would give his translocated chromosome, the rest of the chromosome (that would have been damaged and broken off) and the female would give another one of her chromosomes.
This would then mean that the child would have a whole additional chromosome
What are the types of trisomy
Trisomy 21 - Down syndrome
Trisomy 13 - patan syndrome (this would normally be incompatible with life)
Trisomy 18 - edwards syndrome (distinguished as the children would normally have the rocky bottom feet)
What is reciprocal translocation
This would be when two different chromosomes would break and would attach to each other, but there would be no gain or loss and so this would mean that there would be balance.
What is array-CGH
This is another method more like FISH that would show the imbalances, such as the insertion, deletions and the translocations
How do you prepare and array-CGH
1) metaphase chromosomes, flood them with water so that they burst
2) denature and add the probe, by hybridising them
3) two different types of dna. Reference :green and patient : red
4) add to the tray
5) more green then red shows a deletion
6) more red then green would show an insertion
7) when there would be an equal amount of red and green there would be a yellow colour shown
8) remember that all types of dna would always be added in a 1:1 ratio
Why use cytogenetic
To diagnose or confirm and disorder (prenatal diagnosis or leukaemia diagnosis)
Determining new causes (array-CGH)
Mapping of genes by FISH (gene locations to chromosome bands and the position, ordering and orientation of the chromosome)
What are RFLP
Restriction fragment length polymorphism
This would show how individuals would have the different restriction sites and so would show the polymorphism in the population
What is VNTRS
Variable number tandem repeats
This would be the small repeat sequences in individuals, these would be non-coding but again would show the polymorphism
They would also be able to be used for the DNA-fingerprinting
What are telemetric repeats
Repeats hat would be on the ends of the dna strands.
Telomeres
They would stop the dna strand from unwinding and would shorten during dna replications
Would account for cancer and ageing (shortening of telomeres)
