Allred 38 Flashcards
Q-banding
Quinacrine Fluorescent Staining A/T rich regions Requires fluorescent microscope Fluorescent intensity fades quickly
G-banding
Giemsa
Binds to phostphate groups
Light bands: euchromatin
Dark bands: heterochromatin
Euchromatin
Lightly packed, transcriptionally active; C/G rich
Heterochromain
Tightly packed; rich in satellite sequences; A/T rich;
R-banding
Reverse banding
Dark bands: euchromatin
Light bands: heterochromatin
Better for visualizing chromosome ends
Cytogenetics
Study of the structure and function of the cell; focused on chromosomes
Useful for: Disease and Cancer diagnosis, prenatal amniocentesis to identify chromosomal and genetic disorders
Categories of DNA
Conserved (nonrepetitive):
Intergenic
Introns
Exons
Repetitive:
Transposons
Simple repeats
Large duplications
C0t Analysis
Measures complexity of the genomes by reassociation
C0t Analysis
The procedure involves heating a sample of genomic DNA until it denatures into the single stranded-form, and then slowly cooling it, so the strands can pair back together. While the sample is cooling, measurements are taken of how much of the DNA is base paired at each temperature.
The amount of single and double-stranded DNA is measured by rapidly diluting the sample, which slows reassociation, and then binding the DNA to a hydroxylapatite column. The column is first washed with a low concentration of sodium phosphate buffer, which elutes the single-stranded DNA, and then with high concentrations of phosphate, which elutes the double stranded DNA. The amount of DNA in these two solutions is then measured using a spectrophotometer.
Sattelite DNA
DNA that differs in buoyant density from the rest of the sequence
Both interspersed and tandemly repeated
Very short repeats 2bp - 1500 bp
Makes up >30% of the genome
SINEs
Short Interspersed Nuclear Elements (3-5% of the genome)
E.g. - Alu
300 - 500,000 copies
300 bp of 2 tandemly repeated, similar sequences
Flanked by short Direct Repeats
LINEs
Long Interspersed Nuclear Elements (17% of the genome)
E.g. - L1
1kb - 60kb
Centromere
Repetitive DNA at the Centromere of each chromosome
~500k copies per cell
5-5-2 tandem repeat subunits of 171bp
Telomere Sequences
Required for stability and replication of linear chromosomes
Conserved across species
Tandemly repeated short sequences
Length depends on organism
HFT
Hall Tiny Fragments (1% of the genome)
1k - 2k bp
Associated with expressed genes
Characerized by rare CpG dinucleotide that occurs unmethylated
