L15 - haematopoiesis and leuk

Question 1

What is lymphoid leuk?

Answer 1

Accumulation of immature lymphoid cells as cancer stops maturation

Question 2

What is myeloid leuk?

Answer 2

More common, involves more cells. Can cause a maturation block or increase proliferation

Question 3

What are some genetic changes in leuk?

Answer 3

Loss of chr. (deletion and monosomy)
Gain of chr. (duplication and trisomy)
Altered g.e. (gene fusion)
DNA mutation (point, splice, frameshift, deletion, duplication)

Question 4

How can a chr abnorm be detected?

Answer 4

Karyotype - G band (stop cells in metaphase)

FISH - locus specific analysis

Question 5

Give examples of chr. abnormalities in leuk

Answer 5

Trisomy, monosomy, inversion, insertion, translocation

Question 6

What is a fusion gene?

Answer 6

Breakpoints within or next to 2 genes - creates a hybrid gene with chimeric protein products. If it occurs near a regulatory gene then there will be altered reg of protein product

Question 7

How is a G-band karyotype prepared?

Answer 7

Culture cells and at colcemide - arrests cells in metaphase (longest chr.)
Add hypotonic solution - cells swell - sep chromosomes
Fix cells and stain

Question 8

What are the dark bands?

Answer 8

AT rich, late replicating, gene poor, heterochromatic regions - more removal of protein

Question 9

Light bands

Answer 9

AC rich, early rep, gene rich, euchromatic

Question 10

How is gene rearrangement detected and why is it important?

Answer 10

FISH - use fluoro probes to paint the chr.
Can have centromere, whole chr, locus specific fish painting
Dual colour probes - can look for gene fusion/translocation
There is a clinical need for rapid conf of gene fusion (diag/treat/prognostic)

Question 11

What can translocation of chromosomes cause?

Answer 11

Juxtapos of gene next to regulatory sequence

Altered regulation