Chromosome Analysis: Flow karyotype

Question 1

In this chromosome analysis, suspension of chromosomes is first stained by a fluorescent dye (usually ethidium bromide), and the fluorescence generated by the laser beam in each chromosome is collected in a photomultiplier and stored in a computer.

Answer 1

Flow karyotyping

Question 2

In flow karyotyping, many chromosomes form separate peaks, and the median of each peak provides an accurate and reproducible measure of the ____.

Answer 2

relative DNA content of a particular pair of chromosomes

Question 3

In flow karyotyping, the area under each peak represents ____.

Answer 3

the relative number of chromosomes in each group.

Question 4

What is the lower limit of resolution of flow karyotype?

Answer 4

1–2Mb

Question 5

The technique can be used for assessing variation in individual chromosomes (see Fig. 5.12) and for identifying chromosome aberrations, in particular microdeletions, as its lower limit of resolution is 1–2Mb compared with 4Mb for the light microscope.

Answer 5

Flow karyotype

Question 6

As FACS can also sort chromosomes according to their DNA content, sufficient individual chromo- somes or groups of chromosomes can be collected for the preparation of _____.

Answer 6

chromosome-specific DNA libraries

Question 6

What are the dyes used in dual laser flow cytommtry and their affinities?

Answer 6

Hoechst 33258, which has an affinity for AT-rich DNA
Chromomycin A3, which has an affinity for GC-rich DNA

Question 6

In this subcategory of flow karyotype, chromosomes are stained by a mixture of two dyes and pass sequentially through the laser beams, which allows the fluorescence generated by each dye to be analysed separately. This ultimately allows chromosomes to be resolved not only by their DNA content but also by their AT:GC ratio.

Answer 6

dual laser flow cytommetry