Chromosome Structure, Abnormalities, and Nomenclature Flashcards
Different types of chromosome structure
Metaphase spread
Arrest chromosomes during metaphase (most condensed) to analyze
G-banded karyotyping: add colchicine to halt chromosomes in metaphase and then order them by banding pattern, size, and morphology to identify genetic diseases
What are its limitaitons
Takes a logn time, quality and resolution may be bad
Blood samples are the best quality
FISH - Fluorescence in situ hybridization
Determine the number and location of specific DNA sequences by using a fluorescent probe during high-temp incubation
Can localize genes and directly visualize chromosomal anomalies
Limitations of FISH
High false positive rate due to apparent co-localization fo two signals when viewing a 3D nculeus
Microarrays
Thousands of nucleic acid sequences are arranged in grids and DNA/RNA probes are hybridized to it–> scanner detects complementary binding
Detects smaller deletions and duplications like SNPs or CNVs
Limitation of microarrays
May not detect balanced rearrangements or mosaicism
TErminal deletion
The segment distal to teh breakpoint is completely absent
-> criduchat, Wolf-hirschhorn syndrom
Interstitial deletions
have a starting and ending break point
Ex) Smith-Magenis, Digeorge
Robertsonian translocation
The long arms of 2 acrocentric chromosomes fuse at the centromere and the 2 short arms are lost
Balanced translcoations don’t cause abnormal phenotype
Unbalanced translcoations result in miscarriage, sitllbirth, chromosomal imbalances, chidlren w Down syndrome
A carrier of a robertsonian translocation has
45 chromosomes
Turner and Klinefelter syndromes are chromosomal imbalances that
DONT impair intellectual ability
Individuals who are mosaic have a ___ phenotype
milder
