Chromosomal DNA Flashcards
What is a nucleosome?
Chromatin = DNA + histones wound 2.5x
How are chromosomes packaged in prokaryotes ?
Single naked chromosomes without histones but still supercoiled.
What does DNA polymerase III do?
Catalyses addition and linking of nucleotides into polynucleotide strands.
What converts relaxed to supercoiled DNA in eukaryotes?
DNA gyrases
What converts relaxed to supercoiled DNA in prokaryotes?
Topoisomerases
When is DNA relaxed?
When genes are transcribed / DNA is being repaired/ replicated
What is the process of isolating genomic DNA based on?
Length and relative inflexibility of chromosomal DNA molecules
Why are chromosomes susceptible to physical breakage?
They are very long & double-stranded when makes them relatively inflexible
What is added to chromosomal DNA to get rid of RNA?
Ribonuclease to digest all of the RNA into ribonucleotides
How is DNA isolated?
- larger molecules can be broken
- Gentle cell lysis w/ detergents
- Separate and purify by spooling, dialysis and precipitation
What are detergents?
Surfactants –> lower surface tension
What are the two common detergents used?
SDS: bacterial lysis
DDM: eukaryotic cell lysis
What do detergents do?
-Provide a long aliphatic hydrophobic chain beginning with a methyl group + capped by a charged group.
How does SDS denature protein?
- Charged polar end interrupts protein surface polar + ionic interactions
- Long aliphatic chains gain access to the interior core of the folded protein
- Can bind to inner non-polar amino acid side chains
Which is more efficient at precipitating nucleic acids (Isopropanol vs ethanol)
Isopropanol (only needs 1:1 ratio)
What is epigenetics?
Study of changes in organisms by modification of gene expression rather than alteration of genetic code
What are the 3 systems which initiate epigenetic change?
- DNA methylation
- Histone modification
- Non-coding RNA associated gene silencing
What are some disorders that may come from epigenetics?
cancer, autism, schizophrenia, mood disorders
What is imprinting?
About 1% of genes escape epigenetic reprogramming
What is reprogramming?
The removal of epigenetic tags on sperm and eggs
What does epigenetic inheritance?
Allow an organism to continually adjust its gene expression to fit its environment without changing the code
What can epigenetics be triggered by?
Diet Exercise Drugs, alcohol, smoking Aging Pollutants, toxins Changes to sleep patterns Severe environmental stress Cancer
How does environmental factors trigger epigenetic changes?
Changes in the methylation pattern of cytosine bases in DNA (not the sequence)
