7.2 Transcription Flashcards

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1
Q

Transcription divided into?

A

initiation, elongation, termination

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2
Q

Initiation

A

begins when RNA polymerase binds to DNA and unwinds near beginning of gene

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3
Q

promoter

A

nucleotide sequence lies before gene and allows binding of RNA polymerase

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4
Q

TATA box

A

region of promoter that enables binding of RNA polymerase
- has high percent of adenine and thymine bases

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5
Q

transcription unit

A

part of gene transcribed into RNA

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6
Q

Elongation

A

starts building ss RNA molecule after RNA polymerase binds to promoter and opens DNA double helix
- as RNA polymerase moves alone DNA, unwinds DNA at forward end of enzyme
- RNA molecule temporaitly winds to template; growing DNA strands unwind from DNA and extend from RNA polymerase as single nucleotide chain
- as RNA polymerase passes, DNA double helix forms

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7
Q

coding strand

A

DNA strand not being copied but contains same sequence as new RNA molecule

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8
Q

termination

A

prokaryotes 2 mechanisms:
1. protein binding to mRNA
2. mRNA binds to self and in hairpin loop, stopping transcription
- eukaryotes string of adenines transcribed as uracils on RNA
- nuclear protein binds to polyuracil site and stops transcription, newly synthesized RNA dissociates from DNA template strand

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9
Q

post-transcriptional modifications

A

pre-mRNA vulnerable to enzymes that undergo additional modification before reach nucleus and reach ribosomes
- modification is addition of nucleotides to 3’ end of pre-mRNA molecule
- also beginning of pre-mRNA transcript 5’ cap added by diff enzyme

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10
Q

poly (A) tail

A

chain of adenine added to 3’ end of pre-mRNA

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11
Q

5’ cap

A

sequence of 7 g’s added to start of pre-mRNA; ribosomes recognize site and use it as site of initial attachment

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12
Q

exon

A

sequence of DNA or RNA that codes for part of gene

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13
Q

intron

A

non coding sequence of DNA

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14
Q

spliceosome

A

enzyme protein complex that removes introns from mRNA

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15
Q

small ribonucleoprotein

A

protein binds to introns and signals them for removal

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16
Q

alternative splicing

A

process that produces diff mRNA from pre-mRNA allowing more that one possible polypeptide