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Two strategies for generating an abundance of rRNA
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WVSOM -- Genetics
WVSOM -- Protein Transcription
| Question | Answer |
|---|---|
| Two strategies for generating an abundance of rRNA | Includes multiple copies of rRNA genes Multiple transcripts to be simultaneously produced from each gene. |
| Oscar Miller feathers | Multiple transcripts look like the barbs of a feather |
| Nucleolus | Region of a nucleus where ribosomes are produced. NOT a membrane bound organelle. |
| Each gene encodes how many rRNAs? | 3 |
| What transcribes rRNA | Pol I |
| Pre-rRNA | One large RNA molecule transcribed by Pol I |
| What transcribes a fourth rRNA? | A separate 5SrRNA gene. |
| What transcribes the fourth rRNA? | Pol III |
| Ribonucleoproteins | Proteins that assemble around the rRNA to form the large and small subunits of ribosomes. |
| What composes ribosomes? | RNA and protein |
| What are the post transcriptional modifications of tRNA? | Intron splicing Nucleotide addition Methylation Modifications to produce unusual nucleotides |
| How many loops do tRNA have? | 3 |
| What are the 3 loops of tRNA? | D loop Anticodon Loop TψCG Loop |
| Folding of tRNA | Internal annealing folds tRNA into “clover leaves” |
| What genes make up the small subunit? | 18S |
| What genes make up the large subunit? | 5.8S, 5S, 28S |
| What is the secondary fold of tRNA? | The D and TψCG Loops fold back on each other to generate an L shaped structure |
| Unique properties of RNA polymerase I and Pol III promoters | Unlike Pol II, promoters for rR?NA and tR?NA lack TATA boxes |
| Where are mRNA, tRNA and ribosomes produced? | Nucleus |
| Where does translation occur? | cytoplasm |
| How do components get imported and exported from the nucleus? | nuclear pore complexes |
| What are nuclear pore complexes? | channels embedded in the nuclear envelope. |
| How many different proteins make up nuclear pore complexes? | 30 |
| What are the proteins that make up nuclear pore complexes called? | nucleoporins |
| What mediates transport of factors into or out of the nucleus? | importins and exportins |
| What happens to tRNA when it gets to cytoplasm? | It becomes charged |
| Are tRNA ready for translation in the nucleus? Why? | No. They must be charged in the cytoplasm |
| What enzyme charges tRNA? | aminoacyl-tRNA synthetase |
| What makes tRNA charged? | Binding to an amino acid |
| Where does tRNA bind to amino acids? | 3' OH of tRNA binds with carboxyl group of the amino acid. |
| Does charging of tRNA require ATP? | yes |
| Can amino acids be bound to several tRNAs? | yes |
| Can tRNAs be bound to different amino acids? | NO. Only one tRNA can be bound to an amino acid. |
| How can the cell use only four nucleotides to code for twenty different amino acids? | Every 3 bases in mRNA codes for a different amino acid. |
| Codon | a nucleotide triplet that specifies a particular amino acid |
| Characteristics of the Genetic Code (7) | Triplet unambiguous Degenerate Wobble Colinear Non-overlapping Universal |
| Triplet | every three bases of mRNA sequence, read 5' - 3' |
| Unambiguous | codons only specify one amino acid |
| Wobble | The thrid base of codons that specify the same amino acid varies. The first two are usually identical |
| What is the start cdon? | AUG |
| What amino acid is the start codon | Methionine codon |
| All polypeptides begin with | Methionine (Met) Codon |
| What does the ribosome look for when it grabs mRNA? | It reads down the length in the 5' - 3' direction looking for the AUG triplet. It begins to add amino acids to teh grwoing polypeptide chain at this point. |
| Stop codons | UAA UAG UGA |
| When will the ribosome stop growing the polypeptide chain? | When it gets to a stop codon |
| Polypeptide | a polymer of amino acids. |
| Peptide bond | Carboxyl moiety of one amino acid is bound to the amino moiety of the next |
| Residue | an amino acid in the sequence of a polypeptide |
| directions | during translation the RNA is read 5' - 3' while the polypeptide is synthesiszed from the amino to carboxyl ends |
| What are the 3 stages of the translation pathway? | Initiation Elongation Release |
| Initiation stage | Ribosomes are assembled with an mRNA between the large and small subunits, along with the first aminoacyl tRNA (Met). This tRNA is bound to the P site of teh ribosome. |
| Elongation Stage | Addition of amino acids to the growing polypeptide chain |
| Peptidyl site | P site. a region of the ribosome that binds the tRNA that is attached to the growing polypeptide |
| Aminoacyl site | A site. a region of the ribosome that binds that aminoacyl tRNA for the next amino acid to be bound to teh growing polypeptide. |
| Release Stage | the completed polypeptide, mRNA and both ribosomal subunits all come apart |
| What is protein sorting? | proteins are targeted to specific cellular compartments such as mitochondria, chloroplasts, peroxisomes or rER |
| 5 Principle types of Post translational modification | disulfide bond formation glycosylation cleavage polypeptide forlding multisubunit assembly |
| Where does Post translational modification occur? | ER |
| What is glycosylation? | addition of carbohydrate side chains |
| Where does glycosylation occur? | Golgi |
| Where does cleavage occur? | Golgi and vesicles |
| What mediates proper folding? | helper protiens known as chaperons |
Created by:
tjamrose
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