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IMMS lectures > chromosome abnormalities > Flashcards

chromosome abnormalities Flashcards

1
Q

which tissue types can be cultured (5)

A

blood - T lymphocytes
skin/umbilical cord/placenta
bone marrow
solid tumour
amniotic fluid/chorionic villus

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2
Q

how do you prepare a cell culture

A

take a sample eg blood
add to culture medium + PHA
incubate at 37 C for 48-72 hours
add colcemid
add hypotonic solution
fix cells
cells spread onto slide by dropping
staining
banding
karyotyping

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3
Q

what is the system for naming chromosomes

A

ISCN
International System of Chromosome Nomenclature
eg 46 XX

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4
Q

what are the 2 types of chromosome abnormalities

A

1)numerical - very few that survuve birth
2)structural

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5
Q

what are the 3 types of numerical chromosome abnormalities

A

triosmy - 47,XX+21
monosomy - 45 X
polyploidy - 69, XXY

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6
Q

what are the 4 types of structural chromosome abnormalities

A

translocation
inversion
duplication
deletions

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7
Q

what is the frequency of chromosome abnormalities overall

A

1 in 200

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8
Q

what causes down syndrome

A

extra chromosome 21
triosmy 21

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9
Q

what causes edwards syndrome

A

extra chromosome 18
triosmy 18

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10
Q

examples of sex chromosome abnormalities

A

47, XXY Klinefelter
47, XXX Triple X
47, XYY
48, XXYY or 48,XXXY

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11
Q

what is triploidy

A

when there are three copies of every chromosome instead of the normal two

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12
Q

what causes patau syndrome

A

extra chromosome 13

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13
Q

what is reciprocal translocation

A

structural chromosome abnormality
occur when part of one chromosome is exchanged with another

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14
Q

what is alternate segregate translocation

A

when two normal non-homologous chromosomes and two translocated chromosomes separate into different poles.

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15
Q

what is robertsonian translocation

A

when effectively, the whole of a chromosome is joined end to end with another. This type of translocation involves only chromosomes 13, 14, 15, 21 and 22, because the ends of their short arms have similar repetitive DNA sequences that predispose to their fusion.

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16
Q

what is Cri Du Chat syndrome

A

a chromosomal condition that results when a piece of chromosome 5 is missing

17
Q

what causes prader villi and angelman syndrome

A

both caused by the absence of a limited region of chromosome 15, but differ with respect to the parental origin of the chromosome 15 present

18
Q

what does FISH stand for

A

fluorescence in situ hybridisation

19
Q

how does FISH work

A

use DNA probes labelled with fluorophores
they are hybridised directly to the chromosome preparation or interphase nuclei

20
Q

define cytogenetics

A

refers to the study of tissue, blood, blood marrow, or culture cells in a laboratory, using banding or manipulating techniques to look for changes in the chromosomes, including broken, missing, rearranged, or extra chromosomes. Changes in the chromosomes may be a sign of a genetic disease or condition

21
Q

how is FISH used in cytogenetics (4)

A
  • can count chromosomes in interphase nuclei
  • can look for submicroscopic deletions using locus-specific probes
  • can interpret abnormalities more clearly
  • can look for specific rearrangements such as gene fusion etc in acquired abnormalities
22
Q

what is a microarray

A

a laboratory tool used to detect the expression of thousands of genes at the same time. DNA microarrays are microscope slides that are printed with thousands of tiny spots in defined positions, with each spot containing a known DNA sequence or gene.

improves resolution for detection of cytogenetic abnormaities

23
Q

what is G band resolution on microarrays

A

5-10mb

24
Q

what are constitutional chromosome abnormalities

A
  • occur at gametogenesis
  • affect all cells of the body
  • heritable
25
Q

what are acquired chromosome abnormalities

A
  • changes occur during lifetime
  • restricted to malignant tissue
  • not heritable
26
Q

what is the role of cytogenetics (4)

A
  • confirmation of malignancy
  • classification of a disease type
  • prognosis
  • monitoring
27
Q

what are fusion/hybrid genes

A

breakpoints occur within the 2 genes involved

fusion creates a hybrid gene which gives rise to a chimaeric protein

28
Q

what is deregulation

A

changes in gene expression modify cell behaviour and impair the normal functioning of tissues and organs.
can result in increased transcription and neoplastic growth

29
Q

why are arrays better than microscopy when looking at genome

A

higher resolution

30
Q

why is FISH useful

A

can provide quick results without the need to look at chromosomes

IMMS lectures (22 decks)

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