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Lecture 13

BSCI 283 Lecture Notes - Lecture 13: Polymerization, Nucleophile, Chromosome

Biological Sciences Program
Course Code
BSCI 283
Daniel Stein

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Gene Expression 3/27/17
Gene Expression
o Eukaryotes have genome organized in chromosomes of 2 chromatids with linear
o Prokaryotes have 1 chromosome and plasmids, circular double stranded DNA
o DNA is supercoiled
o Purpose- to store information in genes, represented by boxes on top strand
encoding in that direction on template strand
o The genetic information that defines a species
Chromosomes- sometimes multiple
Sometimes multiple linear chromosome
o In eukaryotes multiple, linear chromosome enclosed in the nucleus plus circular
chromosomes in mitochondria (chloroplasts)
o Bacteria and archaea most have single chromosome, circular double stranded
DNA molecule
o Different genes have different genome sizes
Smallest bacterial genomes:
Carsonella ruddii 160kbp
Mycoplasma genitallium 550kbp
Largest bacterial genomes >13,000kbp
o Ex. E.coli k12 strain: 47000kbp
o Pathogenic O157:H7: 5.6Mb
o Bacillus thurigiensis: 7.8 Mb
o Candidatus Liberibacter asiaticus: 1.23 Mb
o Prokaryotic chromosomes are supercoiled and highly compacted without the
DNA would not fit into the cell
Central Dogma
o DNARNAprotein
Nucleotide Activation
o Nucleotides must be activated by phosphorylation in order to be polymerized
o 3’ hdrol ats as uleophile ad attaks phosphate eter. ’ oaio leaig
group at same time SN2 reaction
o nucleotides are activated with triphosphate
RNA Polymerase
o RNA polymerase core consists of a complex of 4 proteins
o Alpha, alpha’, eta, eta’
o Core is responsible for catalyzing the polymerization of RNA
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