Exam 1 9/14 Nguyen Micro Flashcards
Central dogma
Dna to rna to protein
Purines
A and G
Pyrimidines
C, U, T
A-T has ___ H bonds
2
C-G has ___ H bonds
3
Direction of transcription
5 to 3 prime
Codons
each amino acid is defined by triplet code
Start codon on DNA
ATG
Start codon on RNA
AUG
Stop codon DNA
TAA, TAG, TGA
Stop codon RNA
UAA, UAG, UGA
True or false: bacteria do not contain histones
True
Merodiploid
Partial duplication of chromosome in cell; contains 2 copies of genes
Virulent strains of Vibrio cholerae may contain:
2 chromosomes
1st = essential cellular functions, PAIs
2nd = some essential cell functions, plasmid genes
DNA methylation in humans promotes formation of:
heterochromatin
Histone acetylation promotes the formation of:
euchromatin
Human genes may include what features?
- upstream repressor/enhancer sites
- promoter
- introns and exons
- distant enhancer
True or false: bacteria does not contain mitochondrial DNA or introns
True
Operon
composed of many genes controlled by a common promoter
Cistron
coding gene within an operon
Operons are generally _____
polycistronic
Operons have a common _____ for transcription
terminator
Operon promoter is recognized by:
RNA polymerase (initiates gene or cistronic transcription)
Operator another name
Regulator
Positive control
Inducible
Negative control
Repressible
What is a benefit for bacteria to have operons?
Synthesize all related enzymes “together”; fast and efficient environmental adaptation
Constitutive expression examples in bacteria
Transpeptidase, NAG, NAM
Negative control operon example
Trp operon
Positive control operon example
Lac operon
Which operons are examples of regulated expression?
Trp and Lac operon
Trp operon is expressed by ____, because:
default; trp is often missing
Describe what happens when trp operon is on
- repressor protein unable to bind DNA
- polycistronic mRNA transcribed
- trp A-E make tryptophan synthetase
Function of trp operon
Makes more tryptophan when concentration of tryptophan is low in the cell
If tryptophan is present in the environment, then:
tryptophan triggers repression
- tryptophan binds repressor protein
- tryptophan + repressor bind DNA
- blocks RNA polymerase so it cannot make mRNA
In lac operon, if glucose is low and lactose is available, then:
lac operon is expressed to make lactase
Transcriptional regulation of lac operon
not expressed by default, is inducible; repressor binds to operator so RNA Pol can’t bind to promoter
In lac operon, when lactose is present:
- allolactose protein binds to repressor, released from operator site on DNA
- RNA Pol binds to promoter to allow transcription
Catabolite activator protein (CAP)
Glucose sensor
Hunger molecule
cAMP
E. coli makes ___ when low in glucose
cAMP
Alternative regulator of lac operon
CAP-cAMP