DNA to proteins Flashcards
(57 cards)
what am I:
basic unit of heredity and composed of a sequence of nucleotides in DNA that encodes the synthesis of DNA and generally indue the production of a polypeptide
a gene
what am I:
-a particular physical region of a double-stranded DNA molecule
locus
which experiment allowed the discovery of genes?
the Tatum and Beadle experiment
describe the Tatum and Beadle experiment?
-fungus is grown in minimal media, therefore must be able to synthesize all necessary biological molecules
-fungus is exposed to x-ray to induce mutation of the DNA
-fungus is then grown in rich media
-transfers back to minimal media, some of the fungus cannot grow anymore
-finally can grow if supplement with arginine
what are the amino acids part of the arginine multi enzyme pathway?
-glutamate
-ornithine
-citruline
-arginosuccinate
-arginine
what is the conclusion of the Beadle and Tatum experiment?
a specific stretch of DNA, the gene, encodes for the structure of one enzyme protein
what is the central dogma in biology?
information passes in one direction from the gene (DNA), it is transcribed to m-RNA and translated to amino acids
which strand is transcribed to a single strand m-RNA molecule?
template strand
what is reverse transcription?
to insert their own genetic code into the host genome during infection
true or false: the m-RNA transcript’s sequence is complementary tot he template strand
yes
true or false: prokaryotes have a single RNA polymerase
true
what are the 3 steps of DNA transcription?
1) initiation
2) elongation
3) termination
what is core polymerase?
-composed of alpha and beta subunits
-can synthesize m-RNA from DNA, but cannot initiate transcription
what is holoenzyme?
-combination of the core polymerase with the sigma factor
-combo can accurately initiate synthesis!
what happens during initiation?
a) sigma factor joins the core polymerase to form the holoenzyme
b) sigma factor permits the recognition specific sequences of DNA called promoter at -35 and -10 bp from the start site
c) the helix is open at -10 bp region, and transcription at the start sites at +1 base pair from the start site
d) sigma factor dissociates from the core polymerase
what does initiation rely on?
2 sequences present in DNA called the promoter region
what is the promoter?
-region located before the start signal (not transcribed)
-contains 2 binding sites for sigma factor of the RNA polymerase at -35 and -10 bp before the start site
what happens during elongation?
-promoter clearance
-transcription bubble is then formed as RNA is elongated
-transcription bubble contains RNA polymerase, DNA template strand, and growing m-RNA transcript
-RNA polymerase adds a matching RNA nucleotide to the 3’ end of the m-RNA strand
-after the transcription bubble passes, the now-transcribed DNA is rewound as it leaves the bubble
which direction does m-RNA grow?
5’ to 3’
what happens during termination (prokaryotes)?
the end of transcription unit is marker by terminator sequences that signal “stop” to the polymerase
what are the 2 types of termination (prokaryotes)?
-rho-dependent termination
-rho-independent termination
what happens during rho-dependent termination?
-m-RNA that is produced contains a binding site for the rho factor
-rho factor binds to the sequence and starts climbing up the transcript towards RNA polymerase
-when it catches up with the polymerase, rho pulls the RNA transcript and the template DNA strand apart
another sequence called the transcription stop point causes RNA polymerase to pause and thus helps rho catch up
what happens during rho-independent termination?
-as the RNA polymerase approaches the end of the gene, it hits a region rich in C and G
-RNA transcribed from the region fold back on itself and complementary C and G bind together
-this causes a stable hairpin that causes the RNA polymerase to stall
-hairpin is followed by a stretch of U nucleotides in RNA which match u with A in template DNA
which RNA polymerase in eukaryotes transcribes m-RNA
rna polymerase II
