Chromosomes and abnormalities Flashcards
what phase of mitosis is most useful for chromosome analysis and why?
Metaphase, as the chromosomes are condensed
describe the 7 steps of karyotyping?
- sample is added to a culture medium - + PHA
- incubate at 37C
- Add Colcemid, inactivates spindle fibre formation
- add hypotonic solution, swells the cell so that the chromosomes are more spread
- fix the cells and spread on slide by dropping
- stain
- bandind
how does colcemid inactivate spindle fibre formation?
binds to tubulin protein
what’s an ideogram?
a diagram of a chromosome at different resolutions, shows banding
what does metacentric mean?
the centromere is near the centre
what does centric mean?
the centromere is in the centre
what does acrocentric mean?
the centromere is far away from the centre.
what does trisomy mean?
one extra chromosome
what does monosomy mean?
loss of one chromosome
what does polyploidy mean?
mutiple extra chromosomes
what is translocation?
a chromosomal segment is moved from one position to another either on the same chromosome or a different chromosome
what is inversion?
a region on a chromosome is inverted
what is duplication?
a bit of genetic material is duplicated
whats a nullsomic gamete?
a cell with no genetic material in it
Edwards syndrome causes –>
trisomy 18, short life expectancy a year or less
Patau syndrome causes –>
trisomy 13, significant cleft lip/palate, eye problems, short life expectancy 3 years or less
in order describe these conditions -
- 47 XXY
- 47 XXX
- 45 X
1 = Klinefelter 2 = triple X 3 = Turner
whats a triploid karyotype?
three copies of every single chromosome - significant growth retardation, life expectancy less than a week
whats a reciprocal translocation?
exchange of material between non-homologous chromosomes
what segregation?
where chromosomes separate
what is robertsonian translocation?
between chromosomes where the centromere is right at the top
what does FISH stand for?
Fluorescent in situ hybridisation
how does FISH work?
DNA probed with fluorophores
hybridised directly to the chromosome targeted for a specific region/gene
used to count genes during interphase
what is a microarray?
an analytical method that improves the resolution for the detection of cytogenetic abnormalities.
how does a microarray work?
mix DNA on a slide
contains millions of probes
ratio of colours determines the amount of DNA
what is a constitutional abnormality?
a abnormality that affects every cell - it is inheritable and occurs at gametogenesis
what is an acquired abnormality?
a change that occurs during life, restricted to malignant tissue and isn’t inheritable
what is a fusion gene?
a hybrid gene created when 2 portions of 2 different genes join to form a new protein. or by joining a gene to a different promoter
what is deregulation?
juxtaposition of gene to a regulating gene - altering regulation which can increase transcription and cause neoplastic growth
what is gene amplification?
when a gene is over produced in a cell
what is nondisjunction?
the failure of chromosomes to separate during meiosis phase 1 or phase 2
what does the Poly-A-Tail do?
stops RNA breaking down
what is alternative splicing?
when an extra exon is added or removede in a tissue (usually 10 so abnormal would be 9 or 11)
what is anticipation?
when a repeat gets bigger when passed on a generation so the condition manifests earlier and more severe than before.
what’s a trinucleotide repeat and give examples?
lots of repeated trinucleotides.
Huntingtons CAG, Myotonic dystrophy CTG, Fragile X CGG)
what is a missense?
when one amino acid is exchanged for another (can be pathogenic or not)
