molecular - cytogenetics and FISH

cytogenetics

the study of chromosomes and genetic structure, function and variation related to human disease and hereditary

conventional cytogenetics

it is a whole genome approach, information about each chromosome from dividing cells, detection includes numerical and structural chromosomal abnormalities

g banding

stains the region of DNA that are rich in adenine and thymine

chromosome banding

arrangement of light and dark bands specific to each chromosome

g banding

canonical banding pattern is giemsa stain banding

r banding

inverse of G banding

FISH

targeted approach based on the diagnosis, uses fluorescently labeled oligonucleotide probes and identify abnormalities in bone marrow blood and solid tumors

cryptic translocation

not seen on karyotype and expressed under abnormal conditions

microdeletion

deletion that are too small to be detected by conventional cytogenetics

di george syndrome

microdeletion that causes congenital heart problem, development and learning delay, cleft palate, 22q11.2 deletion

FISH probes

have fluorescent label and need a fluorescent microscopy; complementary genomic target sequence is denatured on metaphase or interphase chromatin using heat