How is genetic information stored across all. eukaryotes, prokaryotes & viruses
Stored as DNA
what is a genome ?
it is a complete set of genetic information in an organism or a cell
where are small compact DNA genomes located ?
in unicellular eukaryotes ( <20mb) & bacteria archea and viruses (<10mb)
where are large compact DNA genomes located ?
in multicellular eukaryotes
which genomes are more compact ; eukaryotes or prokaryote
prokaryotic genomes are more compact
what is majority of the eukaryotic genome made up of ?
non-coding DNA ( non functional DNA ) 38%
What seperates DNA protein coding regions and functional RNA on eukaryotic genomes ?
non coding (non-functional) DNA
what are exons and its percentage in the human genome
coding sequences and ~ 2%
what are introns
non coding regions that must be removing during/after transcription
what is the nucleoid in prokaryotes?
Circular chromosome that is condensed
what are the 4 compartments of the prokaryotic genome ?
- Single chromosome
- nucleoid
- Plasmid DNA
- Nucleoid Associated proteins
what 3 types of DNA in eukaryotes has to be packed in the nucleus ?
- Genomic DNA
- Chromosomal DNA
- Nuclear DNA
Why do we need to compact DNA ?
it is required for cell division and reproduction
what is a chromatin ?
a complex of DNA, histones, proteins that forms eukaryotic chromosomes and packs the DNA)
what does nuclease digest and what does it not and why ?
nuclease digest exposed DNA but not Chromatin DNA due to its protected regions in the nucleosomes
what is the nucleosome and how many base pairs is a fully digested nucleosome?
it is a comprised of core histone octamer and 180 base pairs of DNA and a fully digested nucleosome is 147bp of wrapped supercoiled DNA
how is DNA compacted and how do the histones bind to DNA ?
through histones DNA is compacted and histones are positively charged while DNA is negatively charged so it wraps around histones 2 times and the linker histone seals the turn that is facillated by electrostatic forces
what are 3 things of core octamer of histones made up of?
- Heterodimer (H2A-H2B)
- Heterodimer (H3-H4)
- Charged N tail of lysines that affect chromatin compaction
what 2 function does shaping and compaction of the chromosome require?
it requires the complex of
1. condensin
2. histone core octamer
Brief digestion of eukaryotic chromatin with micrococcal
nuclease gives DNA fragments ~200 bp long. You repeat the
experiment, but incubate the samples for a longer period of
time while you are in class. This longer digestion yields 146
bp fragments. Why?
A) 53base pairs of DNA is not wrapped around a nucleosome
b) 53 base pairs of DNA is unwinds from the nucleosome
c) 53 bases of DNA are not protected
d) nuclease moves or displaces the nucleosome
53 base pairs are not wrapped around the nucleosome as they were exposed and the nuclease digested them
how is DNA wrapped around the nucleosomes and how many base pairs per turn
DNA is wrapped in a negative supercoil that is 10.17 bp per turn.
what is the negative supercoiling of DNA important ?
negative supercoiling of DNA is key as it stabilizes the energy between DNA and the proteins which restrains DNA
what is Heterochromotin and a example
it is condensed chromatin that suppresses transcription; HP1A
what is Euchromatin?
a more open and decondensed chromatin that is gene activating
