Chromosome Analysis: In situ hybridization

Question 1

If an appropriately labelled segment of DNA (a probe) is added to denatured chromosomes on a microscope slide during the process of reannealing, some of the labelled DNA will hybridise to its complementary sequence in the chromosome. Detection of the labelled DNA under the microscope identifies the chromosomal site of its complementary sequence. What is the technique described in this selection?

Answer 1

In situ hybridization

Question 2

In in situ hybridization, these are chemically labelled DNA oligos that can hybridize with prospective complementary sequences in chromosomes.

Answer 2

Probes

Question 2

What are non-isotopic labels that can be used to label probes?

Answer 2

biotin

Question 2

T/F. Initially, radioactive isotopes were used to label DNA probes, but these have been superseded by non-isotopic labels such as ____; this label can be detected by a fluorochrome coupled to ____. Alternatively, the fluorochrome can be coupled to a ____ (e.g. FITC-11-dUTP) used in the preparation of the DNA probe.

Answer 2

biotin; streptavidin; nucleotide

Question 3

This is now a useful method of detecting deletions of individual disease-associated chromosomal regions such as the velocardiofacial syndrome locus at 22q11.

Answer 3

In situ hybridization

Question 4

Locus for the verocadiofacial syndrome.

Answer 4

22q11

Question 5

A useful clinical research technique is to use _____ probes to carry out FISH in order to locate a specific ____ in individuals who have a clinical phenotype and an apparently ____.

Answer 5

bacterial artificial chromosome (BAC); breakpoint; balanced chromosomal translocation

Question 5

FISH is currently being increasingly used clinically in _____ in order to determine the fetal sex and to detect unbalanced translocation products in situations where there is a family history of an ____ genetic condition or a known apparently ____.

Answer 5

pre-implantation genetic diagnosis (PGD);X-linked recessive; balanced parental chromosome translocation.

Question 5

The _____ DNA analysis technique now provides an additional method by which specific deletions can be identified but utilises extracted DNA rather than metaphase chromo- some preparations.

Answer 5

multiple ligation-dependent probe amplification (MLPA)

Question 6

Using BAC to confirm the CHD7 gene on chromosome 8 as an important cause of ____.

Answer 6

CHARGE association

Question 7

_____ is a modification of complex DNA probing in which combinations of several different fluorochromes are used to paint all chromosomes simultaneously in different colours allowing analysis of the whole karyotype in one hybridisation

Answer 7

Multicolour FISH (M-FISH)

Question 7

What is the causative gene for CHARGE association, a syndrome comprising colobomata, choanal atresia, developmental delay and malformations of the heart and ear has which has been confirmed using in situ hybridization using BAC probes.

Answer 7

CHD7 in chromosome 8

Question 7

_____ are probes made from multiple fragments of chromosome-specific DNA from flow-sorted or microdissected chromosomes are available that ‘paint’ the whole chromosome.

Answer 7

Complex DNA probes