6. Genetics Flashcards
nucleoside
sugar plus base
nucleotide
sugar, base, and phosphate
pyrimidine
guanine and adenine
purine
cytosine and thymine
is DNA or RNA more stable?
DNA is more stable
strong G=C content
hydrogen bonds
phosphodiester bonds
hydrogen bonds connect the strands through the bases
phosphodiester bonds are the phosphate to sugar groups
topoisomerases
insert and remove supercoils
negative supercoiling:
twisted in opposite sense relative to right-handed double helix; found in most cells
DNA gyrase
introduces supercoils into DNA via double-strand breaks
positive supercoiling
helps prevent DNA melting at high temperatures
viruses contain either RNA or DNA genomes
-can be linear or circular
-can be single or double stranded
plasmids
double-stranded DNA that replicate separately from chromosome
-usually circular
-generally beneficial for the cell (antibiotic resistance)
-NOT extracellular, unlike viruses
(can be lost)
plasmids are diverse- multiple can exist in one cell
operon
group of genes transcribed together
DNA replication
semi conservative
parent + daughter strand
DNA polymerase I
fills in the gaps (bw okazaki)
removes RNA primers
DNA polymerase III
replicates majority
DNA ligase
reconnects broken DNA strands
transcription in bacteria
produces RNA from a DNA template
mRna
tRNA
rRNA
terminator regions
RNA contains ribose
-uracil
-less stable
polycistronic
multiple ribosomes reading messenger molecule
transcript for more than one gene
RNA polymerases in bacteria archaea and eukarya
bacteria
-1 RNA polymerase
-only need sigma
archaea
-transcription more complex
-require other transcription factors
eukarya
-transcription more complex
-3 RNA polymerase
sigma subunit
recognizes promoter sequences
binds between the -35 region and the pribnow box in the promoter sequence
operon parts
promoter
5’ leader
gene 1
gene 2
gene 3
transcription terminator
go through transcription to form a polycistronic mRNA with ORF 1, 2, and 3
transcription in bacteria: termination of RNA synthesis is
governed by specific DNA sequences
EX: GC-rich sequences with inverted repeat and central nonrepeating segment
rho-dependent termination
rho-dependent termination
rho protein recognizes specific DNA sequences and causes a pause in the RNA polymerase, releasing RNA and RNA polymerase