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metabolic defects

study of this provided evidence that genes specify proteins

transcription and translation

two main processes

DNA synthesizes RNA


RNA synthesizes Protein



triplet in mRNA

exported out of nucleus and be processed

in a eukaryotic cell, mRNA must be

triplet sequence of nucleotides

the smallest units of uniform length to allow translation of all 20 amino acids


three types of RNA


most closely related to DNA


3 letters, looks like this letter


eukaryotes have ____ polymerases

RNA polymerase II

responsible for mRNA synthesis

initiation, elongation, termination

transcription is divided into 3 parts including


RNA must be _____ before it can function

RNA polymerase binds to promotor region, TATA box plays critical role during this

initiation in transcription

helicase unwinds DNA and RNA polymerase adds nucleotides 10 bases long growing 5 to 3 direction

elongation on transcription

terminator sequence stops transcription

termination of transcription


stops transcription


DNA reforms double helix, RNA peels off template DNA (gene)


number of ATP needed for one amino acid

RNA processing

post transcriptional modification is also called

guanine triphosphate

during capping, a modified ____ is added to the 5 end of mRNA

Poly-A tail

20-200 adenine nucleotides added to 3' end of mRNA


also occurs during RNA processing

protects mRNA from hydrolytic degredation

5' cap first function

identifies mRNA to the small ribosomal subunit

5' cap second function

means of protection

both 5' cap and poly-a tail are

inhibit degredation of mRNA in cytosol

first function poly-a

help mrna export from nucleus

second function poly-a

trailer sequence

poly-a tail is seperated from the stop codon by a _____


noncoding sequences that are removed


coding sequences that are spliced together


identify and help bring about the splicing process


catalyzes splicing reactions

rna and protein

make snRNPs

snRNPs and other proteins

make up a splicisome

control gene activity, allow single gene to synthesize different proteins

role of introns


synthesis of proteins


interpreter between base sequence of mRNA and amino acid sequence of protein


different types of tRNA are known


tRNA is around ____ nucleotides long

anticodon base

pairs with codon of mRNA


coordinate the pairing of tRNA with mRNA


ribosomes contain ___ subunits


ribosomes are constructed in the


three sites

aminoacyl-tRNA synthase

an enzyme that catalyzes attachment of an amino acid to its cognate tRNA


number of different types of ATS

activation of amino acid with AMP

first step

attachment of amino acid to tRNA

step two

brings mrna, trna, and ribosomal subunits together

initiation of translation

three-step cycle that adds amino acids one by one to the initial amino acid, requires cooperation of several

elongation of translation

release of the polypeptide chain from the complex

termination of translation

5'cap attaches to small ribosomal subunit, trna carrying met attaches to mrna codon, large ribosomal subunit attaches

process of initiation in translation


site of mRNA codon and tRNA anticodon coupling

P site

holds the tRNA carrying the growing polypeptide chain

A site

holds the tRNA carrying the next amino acid to be added to the chain

codon recognition, translocation

two parts of elongation of translation


tRNA is directed into the A site by an elongation factor then peptide bond forms between adjacent amino acids


amino acid in A site moves to P, mRNA moves through ribosome 5 to 3


termination sequence is encountered, release factor bonds to sequence, release factor seperates polypeptide and tRNA

assemble nucleic acid chains from monomer nucleotides whos order is determined by complementary base pairing to template strand, synthesize 5 to 3 direction

DNA polymerase and RNA polymerase both


DNA polymerase requires a

uses nucleotides with deoxyribose

DNA polymerase

uses nucleotides with ribose

RNA polymerase

transcription factor would not bind to it, so neither would RNA polymerase

if sequence change occured in tata box

help mRNA leave nucleus, prevent from degredation, facilitate ribosome attachment

5 cap and poly-a tail help

gene expression

process by which DNA directs the synthesis of proteins or RNAs

beadle and tatum

one gene one enzyme hypothesis

has ribose, uracil, single strand

RNA is different from DNA in that it


location of transcription

ribosomes, cytoplasm

location of translation

primary transcript

pre mRNA is also known as


unique triplets exist

template strand

coding strand of DNA is called

end of translation

coded by UAA, UAG, UGA

start codon


different codons code same amino acid, but same codon cant code for different amino acid

why is genetic code redundant but not ambiguous

RNA polymerase

enzyme that uses DNA template strand to transcribe mRNA

transcription unit

region of DNA that is transcribed into an RNA molecule

start point

polymerase initiates RNA synthesis at the ____ ____ on template strand


determines which of the two strands of double helix is used for template


promotor extends several dozen nucleotide pairs ___ from starting point

transcription factors

in eukaryotic cells, ____ ____ mediate the initiation of transcription by RNA pol 2

TATA box

DNA sequence in eukaryotic promotors crucial in forming the transcription initiation complex

transcription factors, promotor, RNA polymerase

comprises a transcribtion initation complex


base pairs with nucleotides at specific sites along intron


cuts pre-mRNA releasing intron and at the same time splices exons together

short nucleotide sequences at end of introns

signal for splicing by snRNPs, then snRNA binds to these sites


RNA molecules functioning as enzymes which catalyze reactions during RNA splicing

all biological catalysts are proteins

idea rendered obsolete by discovery of ribozymes

single strand

allows RNA to base-pair with a complementary region in same molecule giving it a 3-D structure

functional groups

some bases in RNA contain _____ ____ that may participate in catalysis

hydrogen bonding

with other nucleic acid molecules adds specificity

single gene may code for multiple proteins

consequence of alternative splicing of mRNA


RNA synthesized from a DNA template


attaches to ribosomes in cytoplasm and specifies primary structure of a protein


shorter than mRNA, 4 base pair regions, 3 loops


gather together with proteins to make ribosomes


rRNA is formed in


nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule

amino acid, codon

____ binds to 3' site of tRNA, ____ binds to 5' site of it


scientists expected to find one aminoacyl-tRNA synthase per codon but fewer have been discovered can be explained by the ____ concept


flexible base pairing occurs at the 3rd base in a codon at the 3 end of an mRNA codon

active site binds amino acid and atp

step one of trna-amino acid joining

atp loses 2 P groups and joins amino acid as AMP

step two of trna-amino acid joining

trna covalent bond to amino acid and displace AMP

step three of trna-amino acid joining

trna and amino acid is released

step four of trna-amino acid joining

smaller, molecular composition

prokaryotic ribosomes are ___ and have different ____

inactivate bacterial ribosomes without affecting eukaryotes

antibiotic drugs can


gives energy for initiation


first amino acid in polypeptide


catalyzes the formation of a peptide bond between the new amino acid in the A site and carbozyl end of the growing polypeptide

release factor

protein that binds directly to stop codon on A site causing addition of water molecule


mechanism termination is accomplished


group of several ribosomes attaached to and translating same messenger rna

protein folding, post-transitional modifications

will result in final form protein

attachment of sugar lipid or phosphate groups, remove amino acids from leading end, chain may be cleaved, chains come together

post translational modifications


binds to the signal peptide halting synthesis momentairly

receptor protein

SRP binds to a ____ in Er membrane which is part of a protein complex that has a membrane pore and signal cleaving enzyme

SRP, signal protein

leaves and pp synthesis resumes with simaltaneous translocation across membrane with ____ ____ remaining attached to translocation complex

signal cleaving enzyme

cuts off signal peptide

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