Cytogenetic technology and nomenclature Flashcards
(28 cards)
What is the purpose of using spindle poisons like colchicine and colcemid in cytogenetics?
To arrest dividing somatic cells in metaphase, allowing easier visualization of chromosomes
This technique is effective because chromosomes are maximally condensed during metaphase.
What is a karyotype?
The number and type of chromosomes present in an individual
A karyotype is often displayed as a karyogram, which is a printed display of chromosomes.
How are chromosomes classified based on the position of the centromere?
- Metacentric
- Submetacentric
- Acrocentric
The centromere’s position affects the length of the chromosome arms.
What does the notation 46,XX represent?
A normal female karyotype
The first number indicates the total number of chromosomes, and XX indicates the sex chromosomes.
What is the significance of chromosome banding techniques?
They help detect structural abnormalities and facilitate the identification of individual chromosomes
Banding techniques were developed in the 1970s to improve karyotype analysis.
What does the term ‘14q32’ indicate in chromosome banding?
The second band in the third region of the long arm of chromosome 14
Subbands are indicated by decimal points, such as 14q32.3.
What is the primary method used for modern chromosome banding?
Giemsa banding (G-banding)
This method involves partial digestion of chromosomal proteins followed by staining.
What is fluorescence in situ hybridization (FISH)?
A technique where a labeled DNA probe hybridizes to specific locations on chromosomes
FISH can detect deletions, duplications, and rearrangements in chromosomes.
What is the resolution capability of FISH compared to high-resolution banding?
FISH can detect deletions as small as 1 million base pairs (1 Mb)
This is more sensitive than conventional banding techniques.
What does comparative genomic hybridization (CGH) detect?
Losses or duplications of whole chromosomes or specific chromosome regions
CGH is particularly useful in cancer research.
What is cytogenomic microarray (CMA)?
A newer technology that uses SNPs for detecting deletions and duplications of less than 20 kb
CMA is now the preferred approach in clinical settings due to its sensitivity.
What is a major limitation of CGH and aCGH?
They cannot detect balanced rearrangements of chromosomes
This includes reciprocal translocations or inversions.
What is the role of high-resolution banding in cytogenetics?
Increases the number of observable bands from about 300 to as many as 800
This allows for the detection of less obvious chromosomal abnormalities.
What is sufficient for analysis of the entire genome using aCGH and CMA?
Less than a microgram of DNA
What are the most commonly used techniques in cytogenetics laboratories?
aCGH and CMA
What does a spectral karyotype demonstrate?
Identification of a rearrangement between chromosomes 2 and 22
In the CGH technique, what do red-labeled and green-labeled DNA represent?
Red-labeled: test DNA from a tumor sample; Green-labeled: reference DNA from normal cells
What indicates the location of duplications or deletions in tumor chromosomes during CGH?
The ratio of green to red signal on hybridized chromosomes
In array CGH (aCGH), what does hybridization of more red-labeled DNA to a probe indicate?
Duplications
In array CGH (aCGH), what does hybridization of only green-labeled DNA indicate?
Deletions
What was indicated by the aCGH test in a patient with DiGeorge sequence?
A deletion of chromosome 22q11
How is the signal intensity for each probe processed in cytogenomic microarray?
In comparison to a normal reference DNA sample
What does a reduction in the log2 ratio indicate in cytogenomic microarray?
An interstitial deletion
What does an increase in the log2 ratio indicate in cytogenomic microarray?
A terminal duplication
