Cytogenetics Oct12 M3 Flashcards
morphologic groups of chromosomes
metacentric, submetacentric, acrocentric
molecule holding chromosomes until anaphase
cohesins
name of structure on chromosomes that the mitotic spindle attaches to
kinetochores
important proteins in kinetochore
CENP proteins
2 important chromosome regions
centromere, telomere
telomere function and how
protect DNA from ligation and degradation. form loop. tell cell not a broken piece of DNA
how telomere changes with time
shortens with cell divisions
name of the phases in meiosis 1
leptotene, zygotene, early pachytene, late pachytene, diplotene, diakinesis
when crossing over occurs at meiosis 1
pachytene stage (early and late)
name of crossing over structure inmeiosis
chiasma
non-disjunction 3 types
2 homologous chromosomes
2 sister chromatids
how mosaicism can happen from non disjunction
if non disjunction at mitosis
constitutional mosaicism def
at least 2 cell lines with diff chromosomal complements in a fetoplacental unit derived from a single zygote
chimerism def
diff cell lines in diff zygotes
common disease where mosaicism taking place
cancer
3 cytogenetic techniques
- chromosome banding
- FISH
- chromosomal microarray
how to obtain metaphase chromosomes
fix cells at metaphase and put them on slide
chromosome banding def
each chromosome has characteristic light and dark bands
staining used in chromosome banding
Giemsa
Robertsonian translocation def
fusion of 2 acrocentric chromosomes
Robertsonian transloc consequence on carrier and progeny
- no conseq on carrier bc normal chrom number
- progeny might get extra copy of a chromosome
balanced structural rearrangements of chromosome, give 3
reciprocal translocation, inversion, Robertsonian transloc
unbalanced rearrangements conseq
affect dosage sensitive genes
banding and karyotyping: good and bad
good: can see balanced and unbalanced rearrangements
bad: limit to resolution
FISH steps
denature DNA, hybridize with labelled probe, post-hybridization wash, vew signal on fluorescent microscope
FISH good and bad
god: high resolution
bad: only see genome complementary to the probe
microarray concept
many FISH at once.patient DNA one colour, test DNA other colour. if mix sequences and colour is in between, shows equal number of genes
microarray good and bad
good: very high resolution
bad: balanced rearrangements can’t be seen
what techniques used to diagnose down syndrome
all three
what banding allows to see in down syndrome
if Robertsonian chromosome (extra copy of chrom 21 on chrom 14)
reciprocal translocation carriers
if reciprocal chromatids don’t segregate together, get + copies and deletions too
reciprocal translocation between chrom 9 and 22: associated disease
chronic myelogenous leukemia
CML cause of problem
BCR and ABL genes rearrangement: constitutively active protein
CML name of anormal chromosome 22 (with not much left)
Philadelphia chromosome
treatment for CML
TKI (Imatinib, Gleevec)
