L17 - chromosomal mutations Flashcards
what is P
short arm of chromosome
what is q
long arm of chromosome
what separates the arms of chromosome
centromere
define telomere
repeated DNA sequence that protects end of chromosomes
TTAGGG
define sub-telomere
region between telomere and protein region of chromosome
role of telomerase?
DNA pol 2 cant synthesise end of lagging strand so telomerase does this
what do we call a chromosome where p&q arm are equal
metacentric
put these in order of shrinking p arms acrocentric metacentric telocentric submetacentric
metacentric
submetacentric
acrocentric
telocentric
what is the most common type of chromosome in humans
submetacentric
what is cytogenetics
study of chromosome variations that cause certain traits / illesses
does
heterochromatin
euchromatin
stain light or dark
heterochromatin - dark
euchromatin - light
what is karyotyping
process of pairing and ordering all of an organisms chromosomes
what is G banding
staining chromosomes with giesma dye after addition of trypsin
shows how condensed the chromosomes are at different times (eg stages of mitosis)
these bands can be used to identify regions of the chromosome
what is FISH
fluorescent in situ hybridization
uses of FISH
- identify chromosomal aberrations
- chromosome gene mapping
explain process of FISH
what do we look for in FISH experiment?
- two fluorescent probes used, one control binds to DNA outside target region, one binds to target region
- did probe bind
- where did probe bind
- if probe also bound to other unexpected regions
define constitutive chromosome abnormality
all tissues have same chromosomal abnormality
define acquired chromosome abnormality
only one organ / tissue has chromosome abnormality
define homogeneous chromosome abnormality
all cells carry abnormality
define mosaic chromosome abnormality
only some cells carry abnormality
define numerical chromosome abnormality
abnormality what changes number of chromosomes (46)
define structural chromosome abnormality
abnormalities include
missing/extra/changed genetic material within a chromosome
list the types of numerical chromosome abnormalities
polyploidy
aneuploidy
what is euploidy
normal no. and sets of chromosomes
what is polyploidy
presence of more than 2 complete sets of chromosomes
eg normal 46, polyploidy 92
what is aneuploidy
additional / missing individual chromosomes
what are the two types of structural chromosome abnormalities
balanced rearrangements
unbalanced rearrangements
describe unbalanced chromosome rearrangements
additional / missing genetic info on a chromosome
eg insertion/deletion
describe balanced chromosomal rearrangements
no gain / loss of DNA
eg translocation, inversion
what is
triploidy
tetraploidy
types of polyploidy
3 sets of chromosomes (69)
4 sets of chromosomes (92)
what are the types of aneuploidy and how many C’s in each
monosomy - 45
trisomy - 47
nullisomy - 44
what is nullisomy
when pair of homologous chromosomes missing
when does non disjunction most frequently occur
anaphase 1
describe translocation chromosome abnormality
portion of one C transferred to another
describe reciprocal translocation chromosome abnormality
segments from two different C exchanged
describe robertsonian translocation chromosome abnormality
entire C arm attached to another C arm at centromere
what is sub-microscopic deletion
deletion of less that 5mb pairs
too small to be detected by microscope
what is inversion chromosome abnormality
portion of chromosome breaks off, turns around then reattaches upside down
genetic info inverted
what is paracentric inversion
an inversion that doesnt include centromere
what is pericentric inversion
inversion that includes centromere
describe insertion chromosome abnormality
part of a C deleted and inserted into another C
what is ring chromosome abnormality
part of C breaks off and forms a ring
can occur with / without loss of genetic info
what is isochromosome chromosome abnormality
where the p arms attach to eachother and q arms attach to eachother instead to pq
what is NAHR and when does it occur
non allelic homologous recomb
between similar sequences of DNA that aren’t alleles
what is uniparental disomy
when 2 copies of a C come from one parent
what are trinucleotide repeats
DNA segment that contains repeat of 3 nucleotides (eg CAGCAGCAGCAG) if this is passed to offspring the no. of repeats may differ
define synteny
genes occurring on same chromosome
what is trisomy 21
down syndrome
