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bio14
| Question | Answer |
|---|---|
| Transcription | copeies information from a dna sequence to a complementary rna sequence |
| Translation | converts RNA sequence to amino acid sequence of a polypeptide |
| RNA differs from dna by | 1 polynucleotide strand sugar is ribose uracil instead of thymine |
| bases of rna pair with a single strand of | DNA except adenine pairs with uracil instead of thymine |
| single strand rna can fold into a | 3d shape by internal base pairing |
| messenger rna | carries a complementary copy of a dna sequence to site of protein synthesis at the ribosome |
| transfer rna | carries amino acids for polypeptide assembly |
| ribosomal rna | catalyzes peptide bonds and provides structure |
| information flows from | dna to rna to protein |
| messenger hypothesis | mrna forms as a complemetary copy of one dna strand in a gene mrna travels from nucleus to cytoplams carrying info-codons transcription-mrna copy is a transcript |
| adapter hypothesis | an adapter molecule that can bind amino acids and recognize a nucleotide sequence-trna adapter molecule contains anticodons complementary to the codons in mRNA |
| continued | tRNA molecules carrying amino acids line up on mRNA in proper sequence from the polypeptide chain-translation |
| viruses | non cellular particles that reproduce inside cells may have rna instead of dna |
| viruses replicate by | transcribing from rna to rna and then makeing multiple copies by transcription |
| HIV is what type of virus | retrovirus |
| retrovirus | a copy of the viruses genome is encorporated into the hosts genome to make more rna |
| synthesis of dna from rna | reverse transcription |
| components needed for transcription | dna template- one of the two strands a nucleoside triphosphate rna polymerase enzyme |
| RNA polymerase | catalyze synthesis of RNA |
| RNA polymerases are processive- | a single enzyme template binding results in polymerization of hundreds of RNA bases |
| unlike dna polymerases, rna polymerases | do not need a primer and lack a proofreading function |
| 3 phases of transcription | initiation elongation termination |
| initiation requires a | promoter |
| RNA polymerase binds to the | promoter |
| promoter tells RNA polymerase | where to start and which strand of dna to transcribe |
| part of each promoter is | the initiation site |
| rna polymerase unwinds | dna about ten base pairs at a time and reads it in the 3' to 5' direction |
| the rna transcript is | antiparallel to the dna template strand and adds nucleotides to the 3' end |
| rna polymerases do not | proofread and correct mistakes |
| termination is specified by | a specific dna base sequence |
| termination happens by | for some genes it the transcript falls away from the DNA template and RNA polymerase. for others a helper protein pulls it away |
| genetic code | specifies which amino acid will be used to build a protein |
| codon | a sequence of three bases- each codon specifies a specific amino acid |
| start codon | AUG- start translation |
| stop codon | UAA, UAG, UGA- stop translation and polypeptide is released |
| there are a total of how many codons | 64 |
| who used artificial polynucleotides to figure out codon sequences | Nirenburg and matthei- led to the identification of the first three codons |
| the genetic code is redundant | for most amino acids there are more than one codon |
| they are not ambiguous | each codon has one amino acid |
| the genetic code is universal | the codons are the same in all organisms |
| except in | mitochondria and chloroplasts and in one group of protists |
| during transcription and translation in eukaryotes | the nucleus splits |
| transcription and translation in prokaryotes and eukaryotes | happen at the same time in the nucleus then the cytoplasm |
| gene structure of eukaryotes and prokaryotes | sequence read in the same order as the amino acid sequence. noncoding introns with coding sequence |
| modifications of mRNA before translation but after transcription | introns are spliced out. 5' cap and 3' poly A tail is added- eukaryotes |
| each eukaryotic gene has one | promoter to which RNA polymerase binds to |
| at the other end is the | terminator to signal the end of transcription |
| noncoding sequence | introns |
| coding sequence | exons |
| primary mRNA script | pre mRNA |
| what happens there | introns are removed from the final mRNA |
| introns _______________ the dna sequence that encodes a polypeptide | interupt but dont scramble |
| the separated exons code for | different domains (functional regions) of the protein |
| G cap is added to the | 5' end - facilitates mRNA binding to the ribosome |
| G cap protects mRNA | from being digested from being digested by ribonucleases |
| poly A tail is added at the | 3' end |
| _____ is the code at the last codon for the enzyme to cut the pre mRNA. Another enzyme comes in and adds 100s of adenine which is the ____ | AAUAA, tail |
| poly A tail role | assist in export from nucleus. stability of mRNA |
| RNA splicing | removes introns and brings exons together |
| newly transcribed mRNA is bound together by | snRNPs |
| consensus sequence | short sequences between exon and intron. snRNPs bind here and near the 3' end of the intron |
| spliceosome | cuts pre mRNA, releases introns, splices exons together to produce mature mRNA |
| beta thelassemia | mutaion may occur in which the sequence is not spliced correctly |
| mature mRNA leaves the nucleus through | nuclear pores |
| TAP protein | binds to the 5' end. then lead the way through the pores while the immature mRNA stay in the nucleus |
| tRNA | links information in the mRNA codons with specific amino aacids |
| for each amino acid there is a | spccific type or species of tRNA |
| two events must occur to ensure that the protein made is specified by the mRNA | tRNA must read mRNA correctly rRNA must deliveramino acids to each corrusponding |
| 3 functions of tRNA | binds to an amino acid then it is charged associates with mRNA molecules interacts with ribosomes |
| 3d shape of tRNA is from | base pairing within the molecule |
| 3' end is where the | amino acids attach and bind covalenly |
| 3d shape of tRNA is from | base pairing within the molecule |
| 3' end is where the | amino acids attach and bind covalenly |
| anticodon | middle of tRNA, site of base pairing with mRNA |
| wobble | the specificity of the base by the 3' end is not always observed which is why they have the same name |
| wobble allows | cells to produce fewer tRNA species but not allow the code to be ambiguous |
| amino-acetly synthases | activating enzyme charges tRNA with the correct amino acid |
| second genetic code | each enzyme is highly specific to one amino acid and its corresponding tRNA |
| amino-acetly synthases | activating enzyme charges tRNA with the correct amino acid |
| amino-acetly synthases | activating enzyme charges tRNA with the correct amino acid |
| second genetic code | each enzyme is highly specific to one amino acid and its corresponding tRNA |
| enzymes have three part active site | they bind a specific amino acid, a tRNA, ATP |
| experiment by benzeme | protein synthase machinery recognizes the anticodon, not the amino acid |
| ribosome | holds mRNA and tRNA together to allow assembly of the polypeptide chain |
| ribosomes can meke | any type of protein |
| ribosomes have ___ subunits | two- large and small |
| the large subunits have | 3 tRNA molecules rRNA molecules and 49 different proteins |
| the small subunit has | one rRNA molecule and 33 proteins |
| ribosomal subunits are held together by | ionic and hydrophobic forces |
| when not active in translation, the subunits | exist separately |
| large subunit has ___ binding sites | 3, A, P, E |
| A | amino acid site binds with anticodon of charged tRNA |
| P | polypeptide site where tRNA adds its amino acid to the growing chain |
| E | exit site where tRNA sits before being released from the ribosome |
| fidelity function | when proper binding occurs, hydrogen bonds form between base pairs |
| if hydrogen bonding doesnt occur | something is incorrect so the tRNA and codon are rejected |
| three steps of translation | initiation elongation termination |
| initiation | an initiation complex forms- tRNA and small ribosomal unit, both bound to mRNA |
| in prokaryotes | rRNA binds to mRNA recognition site from start codon |
| in eukaryotes | the small subunit binds to the 5' cap on the mRNA and moves until it reaches the start codon |
| start codon | AUG- |
| first amino acid | methionine |
| the large subunit joins the complex | the charged tRNA is in the P site of the large subunit |
| Elongation | the second charged tRNA enters the A site |
| large subunit catalyzes two reacion | it breaks bond between tRNA in P site and its amino acid. peptide bond forms between that amino acid and the amino acid in the A site |
| large subunit has petidyl transferase | ir rRNA is destroyed, all activity will stop |
| what supports the idea that catalyic RNA evolved before DNA | rRNA is the catalyst in peptidyl transferase activity |
| when the first tRNA releases its methionine | it moves to the E site and dissociates from the ribosome and can become charged again |
| elongation is assisted by | elongation factors |
| termination occurs | when the stop codon reaches the A site |
| stop codon binds to a | protein release factor- allows hydrolysis of bond between polypeptide chain and tRNA on p site |
| polypeptide chain separeates from | the amino acid and c terminus is the last amino acid added |
| what initiates transcription/ translation | promoter DNA, AUG in the mRNA |
| what terminates transcription/ translation | terminator DNA, UAA, UAG or UGA in mRNA |
| when several ribosomes work together to translate the same mRA | many copies are made |
| a strand of mRNA with associated ribosomes | polyribosome or polysome |
| post translational protein sythesis | the polypeptide emerges from the ribosome and forms a 3d shape |
| signal sequence indicates | where in the cell it belongs |
| amino acid sequence gives set of instruction to polypeptide | stop translation and go to the ER and sythesize there. Finish translation and send to an organelle |
| conformation of signal sequence allows | them to bind to specific proteins- docking proteins on outer membrane organelles |
| receptor forms a | channel that the protein passes through and may be unfolded at this time by chaperonins |
| a nuclear localizer | directs the polypeptide to the nucleus |
| if the nuclear signal was attached | the polypeptide went to the nucleus |
| if the protein is sent to the ER | signal sequence binds to the sgnal receptor particles before translation is done |
| ribosome attaches to | a receptor on the ER and the polypeptide chain either remains in the membrane or passes through a channels into the lumen |
| what removes signal sequence | an enzyme |
| if finished protein enters ER lumen, it recieves signals of two types | amino acid allows protein to stay in the ER. sugars are added or secreted |
| proteolysis | cutting off a long polypeptide chain into final products |
| glycoylation | addition of sugars to form glycoprotein |
| phosphorylation | addition on phosphate groups catlyzed by prtein kinesis. charged phosphate groups change conformation |
Created by:
abrahanm