Ch 8 Microbial Genetics Flashcards
DNA contains _____ which are the instructions for making _______ and functional ___’s.
genes; proteins; RNA
Protein is:
a functional polymer of amino acids
A gene is:
a locus (or region) of DNA that encodes a protein or functional RNA product
Where are genes located in bacteria?
On large circular chromosomes and sometimes also on plasmids
What are plasmids?
Small, extrachromosomal, circular, self-replicating pieces of dsDNA
Are plasmids double or single stranded DNA or RNA?
dsDNA
What shape are plasmids?
Usually circular
Plasmids contain an origin of ________ (ori), but need _____ ________ to _________.
replication; host proteins; replicate
What direction is DNA synthesized in?
5’ -> 3’
Leading strand
synthesized continuously
Lagging strand
synthesized discontinuously in Okazaki fragments
To connect the Okazaki fragments _________ removes _____ _______. Adjacent Okazaki fragments are joined by _____ _______.
DNA polymerase; RNA primers; DNA ligase
How does a phosphodiester bond form?
through dehydration synthesis
Is DNA polymerase III very accurate in dNTP selection?
Yes
Exonuclease proofreading
Pol III and Pol I correct mistakes
Transcription begins at the ________ sequence and stops at the ___________ sequence.
promoter; terminator
3 phases of transcription
initiation, elongation, termination
Transcription initiation
the rna polymerase binds to the promoter region and separates the double helix
Transcription elongation
RNA polymerase travels along the DNA template and synthesizes RNA
Transcription termination
At the end of the gene, RNA polymerase encounters termination signal in DNA. RNA polymerase detaches from DNA and releases the RNA transcript (mRNA).
Translation
the synthesis of a protein (amino acids) guided by the template mRNA (nucleotides)
Start Codon
AUG
Stop Codon
UGA, UAG, UAA
mRNA
encodes proteins
rRNA
forms ribosomes
tRNA
shuttles amino acids to ribosomes
_____ is used by the _______ to _______ the mRNA during protein ________.
tRNA; ribosome; translate; synthesis
What shape is tRNA?
clover shaped loop
The _______ in tRNA is ____________ to the codon in mRNA and directs the addition of specific ______ _____.
anticodon; complimentary; amino acids
What are the three binding sites for tRNA on a 70S ribosome?
Acceptor (A) site, Peptidyl-tRNA (P) site, Exit (E) site
A site
binds incoming aminoacyl-tRNA
P site
contains the tRNA with the growing polypeptide chain
E site
binds a tRNA recently stripped of its polypeptide
Transcription and translation are _______ _________ in eukaryotes but not prokaryotes.
physically separated
mutations
changes in the genetic material (DNA)
mutagen
agent that causes mutation
spontaneous mutation
occur in the absence of a mutagen (during DNA replication)
base substitution (point mutation)
change in one base
silent mutation
no change in the amino acid sequence
missense mutation
results in one changed amino acid in the protein sequence
nonsense mutation
codon is changed to a STOP codon, resulting in a truncated protein
frameshift mutation
insertion or deletion of 1 or more nucleotide pairs
4 Characteristics of Nuceloside Analogs
look like nitrogenous bases, can replace normal base during replication, cause mistakes in base pairing, result in base substitution
Nucleoside analogs can be useful for _______ & ________.
medicine; research
Ionizing radiation (xrays and gamma rays)
causes the formation of ions that can react with nucleotides and the deoxy- backbone
thymine dimers can be repaired by ______ _____ _____
nucleotide excision repair
Photolyases
separate thymine dimers
constitutive genes
expressed at a fixed rate
repressible genes
turn off expression
inducible genes
turn on expression
repressors
bind to regulatory sequences in the DNA and prevent transcription of target genes
activators
bind to regulatory sequences in the DNA and stimulate transcription of target genes
operon
a set of coordinately regulated genes that share a single mRNA
the lac operon is ______
inducible
beta-galactosidase
hydrolyzes lactose into glucose and galactose
lactose permease
a membrane protein that transports lactose into the cell
The lac repressor is _______ _______.
continually expressed
The repressor protein binds to the ________ sequence and blocks the ________ sequence.
operator; promoter
To inactivate the lac repressor, ____________ binds to the _______ protein, making it unable to bind.
Allolactose, repressor
_____ ___________ binds to the lac promoter and transcription proceeds.
RNA polymerase
What accumulates when there is no glucose?
cAMP
cAMP binds to the _____
CAP (Catabolic activator protein)
CAP is now active and stabilizes the binding of ____ _______ to the lac ____________.
RNA polymerase; promoter
2 transcription differences between eukaryotes and prokaryotes
- transcription and translation happen simultaneously in prokaryotes 2. eukaryotes have introns (taken out) and exons
