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60 Cards in this Set
- Front
- Back
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how many strands are used in RNA synthesis
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one of the two dna strand are used as a template
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What are the similarities between RNA and Dna
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- both nucleic acid, same h structure, seq of stacked nucleotides
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Differences between RNA and DNA
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- instead of thyamine, the nitrogenous base used is Uracil
-RNA less stable dues to additonal oxygen - single strand -more looped structures |
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can RNA form double strands?
Right of left handed? # bp per turn |
yes, Rna is usually single strand by can form short double strand regions due to complementary base pairing, CG and AU
- right handed - 11-12 |
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Discuss the thre different structures for RNA
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Complementary- held together by h bonds
-non complementary- some baes are projecting outward from the double strand region - hair pin |
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what contributes to the tertiary structure of RNA
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- base pairing, base stacking, and interactions with ions small molecules and large proteins
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Discuss the three step of Rna syn Transcription
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1)initiation- signal seq ( promoter) - RNA poly attaches to promoter, RNA syn beings
2)elongation-new polynucleotide Rna copy grow in length due to continuing action of RNA poly 3) Termination - RNA polymerase reaches a seq of DNA called a terminator |
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What occurs during the RNA processing
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- add cap and tail
-remove introns (sections of non coding/nonsense seq) -splicing exons together- seq with meaningful info ( coding seq) |
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what is the first step in gene expression
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- transciption ( initiation, elongation, terminationg)
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what are the two fundamental concepts involved in transcription
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-DNA seq provide the underlying info
- proteins recognize these seq and carry out the process |
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at a molecular level what is a gene called
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transcriptional unit
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what strand is actually transcribed in rna transcription
what is the opposite of this strand |
- template strand
- coding strand/sense strand |
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What is the enzyme that catalyzes the synthesis of RNA
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- RNa polymerase
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what is the RNa polymerase holoenzyme coomposed of
what is its function |
- core enzyme - four subunit
- sigma factor - one subunit - bind loosely with the DNA and scan until it encounters the promoter region |
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what does the sigma factor recognize
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- -35 and -10 regions - contains a helix turn helix structure - involved in tighter binding
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What does the binding of the RNA polymerase to the promoter form ?
When the TATAAT box is unwound what is formed? |
- closed complex
- open complex |
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What is the short RNA strand made within? what is release at this point? what step end at this point?
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-open complex
- sigma factor -initiation ends |
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how long is the open complex ?
the rate of RNA synthesis ? |
- 17 bases long
- 43 NT per sec |
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when does termination of Rna Syn occur
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- occurs when the short RNA and DNA hybrid are forced to seperate - releasing the newly made RNA as well as teh RNA polymerase
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What are the two different mechanisms for termination in bacteria
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- rho- dependent termination - req protien (rho)
- rho independent termination - does not req rho |
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Discuss the three different RNA polymerase use for EUC transcription
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RNA poly 1 - transcribes all rRNA genes ( except 5S rRna
RNA poly II- transcribes all structural genes , syn mRNA , transcribes some sRNA genes RNA poly III- all tRNA and 5sRNA |
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what are the three features found in most promoter
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- transcriptional start site, TATA box, and Regulatory elements
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What is the core promoter
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- relatively short , consist of a TATA box - determined the start of transcription, low level of transcription - basal transcription
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Name two regulatory elements
where are they usually located |
- enchancer- stimulate transcription
-silencers - inhibit transcription -50 -100 region |
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name two types of factors that control gene expression based on location
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cis- acting and trans - acting elements
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Basal transcription apparatus consist of
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- RNA pol II and five general transcription factor
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What is the third component
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mediator - mediates interactions between RNA pol II and various regulatory transcription factors; regulates the ability pf TFIIH to phosphorylate CTD
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WHaT are two common mechanism that alter the chromatin structure
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1) covalent modification of histones - amino terminal of histones are modified in various ways ; acetylation, phosphorylation, methylation
2) ATP- dependent chromatin remodeling - energy of ATP is used to alter the structure of nucleosomes and thus make the DNA more accessible |
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what is the initiation complex composed of
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mRNA, initiator tRNA and ribosomal subunits
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WHat is the function of the initiator tRNA
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recognizes the start codon in the mRNA,
start codon is AUG |
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ribosomal binding site is also known as Shine-Dalgarno seq
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- facilitates mRNA binding
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kozak rules
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a consensus seq for optimal start codon recognition
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start codon is
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AUG after the 5' cap
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elongation rates in bacteria and euc
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15- 18 per sec
6 per sec |
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what role does 16S rRNA play
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role in codon anticodon recognition , detects incorrect tRNA
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decoding function
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important in maintaining the high fidelity in mRNA translation
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stop codons
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UAG, UAA, UGA
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release factors
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proteins that recognize the stop codons
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what are the three release factors for bacteria
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RF1 - UAA UAG
RF2- UAA UGA RF3- does not recognize any , bind with GTp to facilitate termination process |
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what is the release factor of EUC
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eRF recognizes all stop codons
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peptide bond
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formed during the cycle of elongation between the last AA in the pp chain and the AA being added
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coupling occurs
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occurins in bacteria b/c it lacks a nucleus allowing translation to complete prior to the completion of transcription
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polyribosome or polysome
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- is an mRNA transcript that has many bound ribosomes in the act of translation
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sorting signal
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directs protein to its correct location
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what are the two types of sorting in EUC
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1) cotranslational sorting - during translation
2) posttranslational sorting- after translation |
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structural gene
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is one that encodes a polypeptide
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the transcription of structural genes yield what product
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messenger RNA
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what percent of genes are structural
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90
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what does messenger RNA do
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bring codons seq to process of protein synthesis contain information
- 3x the NT of AA in protein |
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function of transfer RNA
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- bring AA to protein syn
15 5 of rna production - 75-85 nt in MW is 2.5 x 10^4 or 4S - recognize codon in mRNA , carry Aa specific to that codon |
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waht does the secondary structure of tRNAs exhibit
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cloverleaf pattern
61 tRNA per codon |
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wath is the enzyme that attaches amino acids to tRNA? how many types? what molecules are involves
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aminoacyl-tRNA synthetases, 20 types
molecule: amino acid , t RNA , ATP |
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wobble hypothesis
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-proposed by Crick,first and second positions are standard but third wobbles or moves
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rRNA
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very abunday in protein syn, 7100 nt, 2million for MW, and 80%
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types and location of ribosome in bacteria/ EUC
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- found in cytoplasm ( Bac)
- found in cytoplasm and organelles ( EUC) - |
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what are the three discrete sites of the ribosomes
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peptidyl site, aminoacyl site, and exit site
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describe Mirco RNA
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small , non coding , 20-40 NT, seq specific; post trans regulators of gene activity
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silencing RNAs
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regulators of gene activities
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small nuclear RNA
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90-400 NTs
10- 20 per cell stable half life highly conserved, so functionally important |
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spliceosome I
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- body that does splicing
laregest and most complicated molecular machine |
