BIO-110 FINAL EXAM FLASHCARDS

Where is DNA isolated in eukaryotic cells

the nucleus

where does protein synthesis happen?

in the cytosol and on the rough ER

what does the messenger RNA do

it acts as the link that connects the teo process

Centra Dogma of Molecular Biology states

• DNA codes of RNA

• RNA codes for protein

genetic info…

flows from DNA to RNA to proteins

differences in genotype may cause difference in

phenotype

each possible 3-nucleobase sequence is called a

codon

how many posisible codons do we have

64 possible codons

how many start codons do we have

1 ( which codes fro methionine)

how many stop codons are there

3

the stop codons…

don’t code for an amino acid at all

mRNA is read by

the ribosome 3 bases (1 codon) at a time

therefore deleting 1 or 2 bases in a sequence

shifts all subsequent codons forward

frameshifting can dramatically change..

the amino acid sequence of the protein

the code is redundant meaning…

all amino acids (except 2) have multiple codons

the code is unambiguous meaning..

all codons only code for 1 amino acid

the code does not overlap meaning…

translation happens in a reading like frame which means each codon is read once and never partially

the code is universal meaning..

all codons code for the same amino acids

the code is conservative meaning…

redundant codons often have a sequence that only differs by one nucleobase

DNA is transcribed by what

the enzyme RNA polymerase

for eukaryotes what must happen to RNA before it becomes a mature mRNA

it must be processed

ribosomes translate mRNA into what

protein

DNA is transcribed to make

RNA

mRNA is translated to do what

to make a protein

how are prokaryote mRNAs different from eukaryote mRNAs

prokaryote mRNAs are basically mature right from transcription, and can be translated immediately

transcription of an individual gene can be

switched on or off

genes being transcribed in a cell are being…

expressed

the complete complement of diff proteins in a particular cell are a result of that cell’s

gene expression

gene expression is influenced by

DNA strands many different sub regions

what is the region on a DNA strand in which RNA polymerase binds to called

the promoter (near the start of the gene to be transcribed)

eukaryotic genes contain regions called..

exons and introns

exons code for

portions of the expressed proteins

what are introns

non-coding “spacer” DNA in the intervening spaces

what happens to the introns during RNA processing

they are “spliced” out

During RNA processing in eukaryotic cells, the ends of the pre-mRNA have

a 5’-cap and a 3’-tail added

for eukaryotes transcription occurs…

in the nucleus

for prokaryotes transcription occurs

in the cytosol

RNA polymerase adds what to the 3’end of the nascent RNA strand

ribonucleotides

RNA polymerase only reads from one strand of DNA and this strand that gets read is called

the template strand

DNA sequence is complimentary to…

the template strand

and therefore the DNA sequence matches the

coding strand

similarity of DNA and RNA polymerase

RNA polymerase also builds mRNA molecules in the 5’ to 3’ direction (so the template strand is read in the 3’ to 5’ direction)

differences of DNA and RNA polymerase

• RNA polymerases do not require a primer to begin transcription

• no helicase necessary; RNA polymerase unzips the DNA itself

what are the 3 phases of transcription

initiation, elongation, and termination

in prokaryotes, the protein sigma binds to the RNA polymerase to form what

a holoenzyme, and then it binds to the DNA

what is a holoenzyme

multimeric protein w/ a catalytic subunit, that carries out specific functions and other adaptor or regulatory subunits

what does sigma do

it acts as a regulatory subunit, guiding RNA polymerase to specific promoter sequences on the DNA template strand

what is a promoter

a sequence positioned at the start of a gene

diff versions of sigma are used to

guide RNA polymerase to diff promoter sequences

in eukaryotes basal transcription factor proteins bind to

DNA promoter first (which creates a binding site for RNA polymerase); then RNA polymerase binds

most eukaryotic promoters contain…

a TATA box which is critical for transcription factor binding

what is the initiation of transcription for prokaryotes

• RNA polymerase and sigma form a holoenzyme which then binds to the promoter region

• Sigma recognizes and binds to the promoter

in prokaryotes, the termination signal is coded into an RNA sequence which forms a..

hairpin

the hairpin causes RNA polymerase to

dissociate from the mRNA transcript

in eukaryotes a poly(A) signal in the DNA sequence creates

a binding site for an enzyme to attach and cut the pre-mRNA transcript

RNA polymerase will continue transcribing RNA until….

it eventually falls off of the DNA template

a gene can be transcribed by more than one

RNA polymerase, simultaneously

in RNA splicing for eukaryotes introns must be removed from…

eukaryotic RNA

the pre-mRNA must have the intron sequences….

removed, and the exon sequences ligated to each other in the correct order

an assortment of what binds to pre-mRNA to form what?

small nuclear ribonucleoproteins (snRNPs); spliceosome

pre-mRNA transcript receive a

5’cap and a poly(A) tail from diff RNA processing enzymes

the 5’ cap serves as a recognition signal for the…

translation machinery (ribosomes) and is necessary for initiation of translation

the tail for a pre-mRNA transcript help to do what for the mRNA?

helps to extend the life of it by protecting it from degradation

for translation in prokaryotes, ribosomes translate mRNA into protein sequences before

transcription is even complete and multiple ribosomes can translate one mRNA simultaneously

for translation in eukaryotes mRNAs are exported to the

cytosol

how does the ribosome perform translation of messenger RNA

by matching the nucleotides in each codon w/ complementary nucleotides on a transfer DNA

what does the P site do

holds the tRNA w/ a growing polypeptide attached that is currently transferring its amino acid

what does the E site do

holds a tRNA that will exit

what does the A site do

holds an aminoacyl tRNA until ready to transfer into the ribosome

what are amino acids for protein synthesis carried by

transfer RNAs (tRNAs)

transfer RNAs (tRNAs) have an

anticodon site which is complementary to a specific codon on an mRNA

what does aminoacyl mean

the tRNA is bound to an animo acid

what are tRNAs made by

tRNA synthase proteins

there are fewer ____ than there are ______

tRNAs;codons

3 of the 61 codons that code for amino acids are

stop codons

multiple codons for the same amino acid usually

have the same bases in the 1st and 2nd position

the interior of a ribosome holds how many tRNAs at a time

3

ribosomes contain

proteins and ribosomal RNAs

the active site on the large subunit that catalyzes the formation of the peptide bond is made up of

rRNA, so it is an RNA enzyme or ribosome

how many subunits do ribosomes have

2

what does the small subunit of a ribosome do

it holds the mRNA in place during translation

what does the large subunit of a ribosome do

it is where the peptide bonds form

what are the 3 phases of translation

initiation, elongation, and termination

during translation what happens

3 tRNAs line up within ribosome based on the mRNA codons sequence

• tRNAs are contained in the A-P-E sites

what do initiation factor proteins do in first phase of initiation for prokaryotes

secures the mRNA transcript to the small subunit of the ribosome

what happens in the second phase of initiation for prokaryotes

proteins guide the first tRNA anticodon to where it will base pair w/ start codon

what is the first amino acid for prokaryotes

a modified methionine, f-Met

what happens in the third phase of initiation for prokaryotes

initiator tRNA is in place where the large subunit can bind to the small subunit, completing the initiation phase

what happens in the first phase of elongation for prokaryotes

second tRNA is funneled to the ‘A’ site and checked for a match

what happens in the second phase of elongation for prokaryotes

once correct tRNA is bound, formation of a peptide bond between amino acids on tRNA is catalyzed

• the bond between ‘P’ site tRNA and its amino acid is catalyzed

what happens in the third phase of elongation for prokaryotes

• tRNA is then translocated to the next site in A-P-E progression

• polypeptide is held in place by bond to ‘P’ site tRNA

what happens in the fourth phase of elongation for prokaryotes

process is repeated for new tRNA match in the ‘A’ site

what happens in the fifth phase of elongation for prokaryotes

• another peptide bond is formed + another amino acid tRNA bond is hydrolyzed

what happens in the sixth phase of elongation for prokaryotes

• initiator tRNA is ejected from ‘E’ site as the tRNAs translocate thru the A-P-E progression

elongation process in translation is repeated until

the ribosome gets to the STOP codon

what happens in termination phase part 1 prokary

begins when STOP codon is reached, a proteins called a release factor binds to STOP codon in ‘A” site

what happens in termination phase part 2 prokary

nascent polypeptide is released

what happens in termination phase part 3 prokary

termination ends with the dissociation of the large and small subunits, and the release of the mRNA transcript

how is eukaryote translation diff from prokaryotes

there are small diff in initiation phase