Chromosomes and cytogenetics Flashcards
(17 cards)
Nucleosome components
DNA wrapped around octamer core of 8 histone proteins H2A H2B H3 H4
H1 histone protein
attaches nucleosome and linker DNA
stabilises structure and recruitment compacts DNA
folding of DNA and nucleosomes
30nm diameter fibre further compacts with attachment to protein scaffold
barrier protein
prevents spread of heterochromatin into euchromatin
loss of barrier protein
chromosomal translocation
position effect variegation
structural heterochromatin
contains repetitive DNA sequences known as satellite DNA found in structural elements such as centromeres and telomeres
telomeres
cap ends of chromosomes
prevent fusion of chromosomes
bound by shelterin protein complexes
structure of telomere sequences
10-15kb
short tandem repeats
5’-TTAGGG-3’
G strand/tail and C strand
formation of T loop
3’ overhang of G strand loops back and invades double stranded telomeric DNA
prevents chromosome end being recognised as a break and prevents degradation
shelterin complex
promotes and stabilises T loop
colcemid
disrupts mitotic spindle to get cells in metaphase for study
hypotonic treatment
causes cells to swell and chromosomes to spread out
best stage of mitosis to view chromosome detail
prometaphase (slightly less compact than in metaphase)
localisation on chromosomes
p arm (short)
q arm (long)
numbered from centromere outward
FISH
colcemid treatment>hypotonic solution>resuspended in methanol to preserve cell structure>place on slide and fix with formaldehyde>heat denaturation>hybridise with fluorescently labelled oligonucleotide probes>DAPI staining>imaging and analysis
chromosome painting
large cocktail of probes used
SKY (spectral karyotyping)
entire set of chromosomes can be analysed
