Chromosome Structure and Karyotypes Flashcards
What are fragile sites?
Non-staining gaps, occasionally observed in characteristic sites on several chromosomes
Only clinically significant fragile site is on the X chromosome and causes Fragile X syndrome
What is fragile X syndrome?
Mutation in FMR1
Causes mental impairment, ADHD, anxiety, Autism, Long facial features, hyperextensible joints
What is a centromere?
region of a chromosome to which spindle traction fibers attach during mitosis and meiosis
What is a metacentric chromosome?
Chromosome with a centrally placed centromere
What is a submetacentric chromosome?
a chromosome with a centromere closer to one end than the other
What is an acrocentric chromosome?
A chromosome with a nearly terminal centromere
What is satellite DNA?
And fraction of the DNA that differs substantially in base composition (AT or GC rich)
Long series of short tandem repeats clustered around centromeres
What is minisatellite DNA?
repeat length of 7-100bp, highly polymorphic e.g. telomeric repeats
What is microsatellite DNA?
Tandem single, di-, tri- and tetranucleotide repeat base sequences located throughout the genome
What type of microsatellite DNA is associated with disorders?
Trinucleotide repeats in or near genes.
E.g. huntington’s and fragile X syndrome
What are SINEs?
Short Interspersed Nucleotide Elements
E.g. Alu repeats
What are LINEs?
Long interspersed nucleotide elements
E.g. L1 - 17% of human genomic sequence
What is a karyotype?
describes the chromosome constitution in terms of the total number of chromosomes and the sec chromosome constitution
Autosomes are listed from largest to smallest
How is the location on a chromosome named?
Chromosome
Arm
Region
Band
What is Giemsa (G)-banding?
Stain used to view chromsomes under normal light photo-microscopy
Produces light and dark bands
What is Quinacrine (Q)-banding?
Fluorescent dye that binds to AT-rich sequences preferentially
Viewed by fluorescent microscopy
What is R (Reverse)-banding?
Stains an opposite banding pattern from the other two.
What is C (Centromeric)-banding?
Stain binds to centromeres
What is High-Resolution banding?
G or R banding performed at an early stage of mitosis when chromosomes are relatively uncondensed.
Useful in detecting subtle structural abnormalities
What is Fluorescent in situ Hybridization? (FISH)
A labeled chromosome-specific DNA segment is hybridized with metaphase then visualized under a fluorescent microscope
What is spectral karyotyping?
Uses multiple fluorescent probes specific for sequences on each chromosome to generate a specific color for each chromosome.
What is comparative genomic hybridization?
Test and control DNA are labeled with fluorophores, then hybridized to normal metaphase chromosomes. Deletions or additions alter the color ratio.
