Chapter 5: Principals of Clinical Cytogenetics Flashcards
What are Clinical Cytogenetics?
the study of chromosomes, their structure, and their inheritance
Giemsa stain ~400 bands/haploid karyotype at metaphase
G banding
stain with quinacrine mustard, results in
a specific pattern of bright and dim bands under the
fluorescent microscope (bright = dark after G banding)
Q Banding
reverses the usual white and black pattern
seen with G- and Q banding; requires heat treatment ->
is the standard method in many labs in Europe
R Banding
central centromere and equal arms
metacentric
off-center centromere
submetacentric
centromere near one end
acrocentric
What are the acrocentric chromosomes?
13, 14, 15, 21, 22
What are the satellites on the acrocentric chromosomes?
small distinctive masses of chromatin attached to the short arms by short stalks
What stains the centromere region and other regions of constiutive heterochromatin?
C banding
What is fragile site detection?
- It identifies non-staining gaps to observe fragile sites.
- It is usually necessary to expose cells to growth conditions or chemicals that alter or inhibit DNA synthesis
probes hybridize along the entire chromosome or chromosome arm
chromosome painting
This is used to diagnose specific deletions or rearrangements and evaluates the karyotype of all 24 chromosomes
spectral karyotyping (SKY)
-cells or individuals with an abnormal number of
chromosomes (not 46)
Heteroploid
-exact multiple of the haploid (n) chromosome number,
have the complete normal chromosome complement (46) that
is characteristic of humans
Euploid
-any multiple of the basic haploid chromosome number
other than the diploid number 3n=69, 4n=92
Polyploid
-any other abnormal number
Aneuploidy
2n + 1 or 47
Trisomy
2n -1 or 45
Monosomy
4n or 92 chromosomes
Tetraploidy
-46 chromosomes from the mother-spontaneously aborted earlier in pregnancy
Digynic
-46 chromosomes from the father -> make up 65-75% of cases -> develop an abnormal placenta that is classified as a partial hydatidiform mole
Diandric
-a union of two or more digits that occurs in humans often as a hereditary disorder marked by the joining or webbing of two or more fingers or toes
Syndactyly
What is a mole?
the placenta is converted into a mass of tissue resembling a bunch of grapes called a hydatid cyst ->no fetus or small atrophic fetus present
