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BIO 211 Chapter 16, Section 2
Transcription and Translation: Transcription & RNA Processing in Eukaryotes
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Biology
12/01/2010

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Term
basal transcription factors
Definition
proteins that initiate eukaryotic transcription by matching the enzyme with the appropriate promoter region in DNA; • analogous to the function of sigma proteins in bacteria, except that basal transcription factors interact with DNA independent of RNA polymerase
Term
TATA box
Definition
located 30 base pairs upstream of the transcription start site; some of the promoters recognized by pol II don’t contain a TATA box
Term
exons
Definition
regions of eukaryotic genes that are part of the final mRNA; they are expressed
Term
introns
Definition
untranslated stretches of eukaryotic genes; they are intervening; cause eukaryotic genes to be much longer than their corresponding mature RNA transcripts
Term
primary RNA transcript
Definition
generated by transcription of eukaryotic genes by RNA polymerase; contains introns and exons
Term
splicing
Definition
process by which introns are removed from growing RNA strand; occurs while transcription is still under way; results in an RNA that contains an uninterrupted genetic message; catalyzed by snRNPs/RNA molecules in the spliceosome (catalytic RNA molecules are called ribozymes)
Term
small nuclear ribonucleoproteins (snRNPs)
Definition
catalyze splicing; small complex of proteins and small RNAs
Term
spliceosome
Definition
multipart complex formed by many snRNPs and other proteins
Term
5' cap
Definition
made of 7-methylguanylate and three phosphate groups; serves as recognition signal for translation machinery
Term
poly(A) tail
Definition
long tract of 100-250 adenine nucleotides; added at 3' end of RNA; not encoded on template strand; extends life span of mRNA by protecting message from degradation by ribonucleases in cytosol
Term
splicing
Definition
begins when initial snRNP binds to 5' exon-intron boundary; spliceosome forms; intron forms a loop with an adenine ribonucleotide at its base, which then cuts the loop; phosphodiester bond links exons on either side, completing splicing; introns usually degraded to ribonucleotide monophosphates
Term
adding caps and tails
Definition
enzymes add 5’ cap to 5’ end of RNA emerges from RNA polymerase; after addition of cap and tail, processing of the primary RNA transcript is complete – product is mature mRNA; 5’ and 3’ untranslated regions help stabilize mature RNA and regulate its translation
Term
transcription in bacteria vs. eukaryotes
Definition
similar in that RNA polymerase doesn't bind directly to promoter sequences by itself (basal transcription factors); bacteria: single sigma protein binds to promoter and initiates transcription & eukaryotes: many basal transcription factors required to initiate transcription (complex machinery to start transcription); eukaryotes: three distinct types of RNA polymerase instead of one; eukaryotes: promoters in eukaryotic DNA much more diverse and complex than bacterial promoters - many of the eukaryotic promoters recognized by pol III include TATA box (pol I and pol III interact with entirely different promoters); eukaryotes: transcription is followed by several important RNA processing steps that result in production of an mRNA that leaves the nucleus; eukaryotes: genes don’t consist of one continuous DNA sequence that codes for a product, as do bacterial genes (• regions of eukaryotic genes that code for proteins come in pieces that are separated by hundreds or thousands of intervening DNA bases)
Term
three distinct types of RNA polymerase in eukaryotes
Definition
RNA pol I, pol II, and pol III – each transcribe a discrete class of RNA; only RNA pol II transcribes genes that code for proteins (produces mRNA); pol I makes large RNA molecules found in ribosomes; pol III manufactures one of the small RNAs found in ribosomes and tRNAs
Term
major differences between bacterial and eukaryotic transcription
Definition
slicing and addition of caps and tails
Term
protein-coding regions of eukaryotic genes are interrupted by ____
Definition
stretches of noncoding DNA
Term
translation occurs in the _____
Definition
cytoplasm
Term
primary function of RNA polymerase II is _______
Definition
transcription of protein-coding genes
Term
TATA box of the eukaryotic promoter is analogous to the _____ of the prokaryotic promoter
Definition
-10 box
Term
[image]
Definition
Term
snRNPs
Definition
[image]
Term
transcription in eukaryotes vs prokaryotes
Definition
[image]
Term
Sharp - tried to figure out how DNA templates are transcribed
Definition
heated DNA molecules enough separate two strands; single-stranded DNA incubated with mRNA encoded by the sequence; idea was to promote base pairing between mRNA and single-stranded DNA; expected mRNA to form base pairs with the DNA that was the template for its synthesis; instead, parts of DNA formed loops; interpreted these loops as stretches of nucleotides that are present in DNA template strand but not in corresponding mRNA
Term
Britten tested hypothesis that ribosomes were site of protein synthesis
Definition
pulse-chase experiment to label a population of molecules as they are produced; fed radioactive sulfate (35SO4-2) to E. coli; expected cells to incorporate radioactive sulfur into amino acids that contain sulfur (methionine and cysteine) and then into newly made proteins; followed by large excess of nonradioactive sulfate; radioactive signal was associated with ribosomes for a short period of time, then found in proteins not in ribosomes; proteins are synthesized at ribosomes and then released
Term
in bacteria, ribosomes attach to mRNAs and begin synthesizing proteins even before _______
Definition
transcription is complete
Term
attachment of an amino acid to a tRNA requires ________
Definition
an input of energy in form of ATP
Term
discovery of basal transcription factors
Definition
purified RNA polymerase from human cells, added template DNA and analyze RNAs produced; RNA polymerase was found copying at random locations on template DNA instead of at promoter regions; when RNA polymerase was alone, both strands of DNA transcribed instead of one; made them think there was a sigma-like protein required for normal transcription; to test this, added proteins one or a few at a time and recorded which ones enabled RNA polymerase to bind to promoters and correctly transcribe the template strand