Lecture 11: The Central Dogma of Biology

describes flow of genetic info, DNA to RNA to proteins

central dogma of molecular biology

DNA to RNA, mRNA synthesis

transcription

RNA to protein

translation

ribonucleic acid, single stranded

RNA

mRNA, tRNA, rRNA

what are the three types of RNA?

direct copy from DNA

messenger RNA (mRNA)

brings amino acids to ribosomes during translation

transfer RNA (tRNA)

forms part of the ribosomes

ribosomal RNA (rRNA)

contains uracil instead of thymine and ribose instead of deoxyribose

how does RNA differ from DNA?

enzyme responsible for transcription, unwinding DNA

RNA polymerase

RNA polymerase binds to DNA at promoter region

initiation

beginning part of gene

promoter

RNA polymerase adds RNA nucleotides in 5’ to 3’

elongation

completed mRNA synthesized, RNA polymerase breaks off

termination

strand of DNA being read

template strand

strand of DNA not read

coding strand

turns on promoter by binding to it

transcription factor

beginning, to the left of gene

upstream

end, to the right of gene

downstream

nucleus

where does transcription take place in eukaryotes?

cytoplasm

where does transcription take place in prokaryotes?

cytoplasm

where does translation take place?

triplet of bases, determines the amino acid

codon

AUG start codon

which codon initiates translation?

50s

prokaryote large ribosomal subunit

30s

prokaryote small ribosomal subunit

60s

eukaryote large ribosomal subunit

40s

eukaryote small ribosomal subunit

complimentary to mRNA codon, found on tRNA

anticodon

methionine

AUG

UAA, UAG, UGA

stop codons

20

how many amino acids are there?

EPA

what are the three hollow chambers in the large ribosomal subunit (left to right)?

the first tRNA

initiator tRNA

use chart and mRNA

how are codons translated to amino acids

intervening sequences of bases that do not code for protein

intron

coding regions of genes that will be translated into protein

exons

remove introns before translation

spliceosomes

eukaryotes

where are introns found?

changes in genetic code

mutation

chemicals, UV light, radiation

what are some factors that increase the frequency of mutations?

a change in one base in a codon

point mutation

silent

what do you call a point mutation that still ends up with the same amino acid?

nonsense

what do you call point mutation that causes a stop codon?

missense

what do you call a point mutation that causes a completely different amino acid?

new amino acid shares similar properties with original amino acid

conservative missense

new amino acid does not share similar properties with original amino acid

non-conservative missense

alter reading frame of DNA through insertion/deletions

frameshift mutation

first enzyme recognizes error and removes it, second enzyme places correct bases and seals gap

excision repair of mutations

prokaryotes

what type of microbe exhibits operons?

coordinated set of genes regulated as single unit, permits genes for particular metabolic pathway by same regulatory element

operon

inducible and repressible

what are the two categories of operons?

transcription from operon is turned on by substrate

inducible

transcription from operon is turned of by product synthesized

repressible

normally turned off

is the lac operon usually turned on or off?

lactose

how is the lac operon turned on?

inducible

what type of operon is the lac operon?

regulator, control locus, structural locus

what are the three features of the lac operon?

gene that codes for protein capable of repressing operon

regulator

composed of two areas, the promoter and operator

control locus

sequence that acts as on/off switch for transcription

operator

made up of three structural genes coding for different enzymes needed to catabolize lactose

structural locus

attaches and inactivates repressor, allowing transcription

how does the inducer turn on the operon?

on

is the arginine operon usually turned on or off?

arginine

what turns the arginine operon off?

repressible

what type of operon is the arginine operon?

inactive

is the arg repressor synthesized in its active/inactive form?

active

is the lac repressor synthesized in its active/inactive form?

activates repressor when arginine accumulates

corepressor

arginine activates repressor, repressor attaches to operator and blocks RNA polymerase

how does arginine turn the operon off?