Clinical Cytogenetics Flashcards
What is the p arm?
The shorter arm in a chromosome
*Centromere in the middle
What is the q arm?
The longer arm in a chromosome
What is metacentric?
The centromere is a little off set
What is Submetacentric?
The centromere is closer to the end toward the p arm
What is Acrocentric?
The centromere is very close to the end of the p arm
What is telocentric
The centromere is all the way to the end of the p arm (No p arm)
*No telocentric in HUMANS (only mice)
What is Karyotype?
- Arrange chromosomes by size and position of centromere (arranged in descending order)
- 46 chromosomes (diploid)
- 22 pairs of autosomes
- 2 sex chromosomes
*Ideogram is organized by size
What is Giemsa or G-banding?
- Pretreat with typsin to digest protein
- Stains AT rich region
- Inexpensive
What are 3 types of stains for visualizing chromosomes?
- Giemsa or G banding
- Quinacrine or Q-banding
- Reverse or R-banding
What is Quinacrine or Q-banding?
- Stains AT rich regions
2. Visualize with ULTRAVIOLET LIGHT
What is Reverse or R-banding?
- Uses Giemsa
2. Chromosomes treated at HIGH TEMPERATURE and LOW pH
What is Aneuploidy?
Change in the copy of individual chromosomes (Trisomy 21)
What is Fluorescent In Situ Hybridization (FISH)?
Labeling a region with a fluorescent probe detected with a fluorescent microscope
What is Chromosome Painting or Spectral Karyotyping (SKY)?
Labeling for each chromosome with a separate color detected with a spectrophotometer
How do you identify a chromosome?
- By Chromosome number
- Region
- Band
- Sub-band
Ex: Chr 16p11.2
a. Chromosome 16
b. Region 1
c. Band 1
d. Sub-band 2 on the p arm
What are 3 structural changes in chromosomes?
- Deletions/Addition
a. Single nucleotides
b. Several nucleotides
c. Microdeletion syndromes - Duplications
- Rearrangements (translocation: one piece of a chromosome gets stuck to another)
What is Rearrangements?
- Two types
a. Balanced
b. Unbalanced
What is Balanced rearrangement?
- All genetic information is present in this individual
- However, a problem might be present in the offspring
- Reciprocal translocation