371430
| Question | Answer |
| transcription | info in a DNA sequence (a gene) is copied into a complementary RNA sequence |
| translation | RNA sequence is used to create the amino acid sequence of polypeptide |
| 3 types of RNA | 1. mRNA 2. rRNA 3. tRNA |
| mRNA | messenger- travels from the nucleus to the cytoplasm to be translated into a polypeptide *nucleotide sequence determines order of amino acids built by ribosome. |
| rRNA | ribosomal- catalyzes the peptide bond formation between amino acids to form a peptide |
| tRNA | transfer- can bind a specific amino acid and recognize a specific sequence of nucleotides in mRNA *recognizes which amino acid should be added next |
| Transcription Requires: | 1. DNA template 2. Nucleoside triphosphates 3. RNA polymerase enzyme |
| RNA polymerase | catalyze the synthesis of RNA from the DNA template -> does NOT require a primer |
| 3 steps of transcription: | 1. initiation 2. elongation 3. termination |
| initiation (transcription) | requires a promoter which "tells" the RNA polymerase two things: 1. where to start 2. which of the 2 DNA strands to transcribe |
| elongation (transcription) | RNA polymerase unwinds the DNA about 13 base pairs at a time and reads the template strand 3'->5' and then adds nucleotides that are antiparallel |
| termination (transcription) | a particular base sequence calls for the end |
| coding regions | sequences within a DNA molecule that are expressed as proteins |
| introns | noncoding sequences |
| extrons | coding sequences |
| pre-mRNA | contain both introns and exons prior to removal of introns |
| nucleic acid hybridization | 1. DNA denatured and strands separated 2. single-stranded nucleic acid from another source is incubated with denatured DNA |
| RNA splicing | removes the introns and splices the exons together |
| consensus sequences | short stretches of DNA that appear with little variation in many genes (between exons and introns) |
| snRNPS (small nuclear ribonucleoprotein particles) | binds the consensus sequences after the pre-mRNA is transcribed |
| spiceosome | a large RNA-protein complex that cuts the pre-mRNA, releases introns, and joins the ends of the exons together |
| alternative splicing | results in different mRNA and different polypeptides from a single gene because sometimes exons get spliced |
| Modifications at the ends of pre-mRNA | 1. 5' cap 2. poly A tail |
| 5' cap | added to 5' end of pre-mRNA as it is transcribed, chemically modified version of GTP, protects it from being digested |
| poly A tail | added to 3' end of pre-mRNA at the END of transcription, assists in export of mRNA from the nucleus |
| codons | nonoverlapping three-letter "words" that specify for a particular amino acid |
| start codon | starts translation AUG |
| stop codons | terminate translation UAA, UAG, UGA |
| silent mutations | can occur because of the redundancy of the genetic code |
| missense mutations | change in amino acid sequence |
| nonsense mutations | results in a premature stop codon |
| frame-shift mutations | insertion or deletion of one or more base pairs within the coding sequence |
| 2 events that must occur for the protein to be made correctly: | 1. tRNA must chemically read each mRNA codon correctly 2. tRNA must deliver the amino acid that corresponds to the mRNA codon |
| 3 functions of tRNA: | 1. tRNAs bind to particular amino acids 2. tRNAs bind to mRNA 3. tRNAs inteact with ribosomes -> each mRNA codon binds to just one tRNA species, carrying a specific amino acid |
| anticodon | complementary to the mRNA codon for the particular amino acid that the tRNA carries |
| 3 sites of large subunit of ribosome | 1. A 2. P 3. E "APE" |
| A site | amino acid- where the charged tRNA anti-codon binds to the mRNA codon, thus lining up the correct amino acid to be added to he growing polypeptide chain |
| P site | polypeptide- where the tRNA adds its amino acid to the polypeptide chain |
| E site | the tRNA,, having give up its amino acid, resides before being released from the ribosome to begin the process again |
| fidelity function | ensures that a charged tRNA with the correct anticodon binds to the appropiate codon in the mRNA |
| 3 steps of translation | 1. initiation 2. elongation 3. termination |
| initiation complex | consists of charged tRNA and a small ribosomal subunit, both bound to the mRNA |
| initiation (translation) | 1. the small ribosomal subunit binds to its recongnition sequence on mRNA 2. tRNA binds to the start codon 3.large ribosomal subunit joins the initiation complex, occupying the P site |
| elongation (translation) | 1. the anticodon of an incoming tRNA binds to the codon at the A site 2. Pro is linked to MEt by peptidyl transferase activity of the large subunit 3. Free tRNA is moved to the E sites, and then released, as the ribosome shifts by one codon, so that the growing polypeptide chain moves to the P site |
| termination (translation) | ends when a stop codon enters the A site: 1. release factor binds to the complex when a stop codon enters the A site 2. the release factor dsconnects the polypeptide from the tRNA in the P site 3. the remaining components separate |
| polyribosome/ polysome | an assemblage consisting of a strand of mRNA with its beadlike ribosomes and their growing polypeptide chains occurs when a ribosome has moved away from the translation site and a second one can come in, and so on... |
| signal sequence | short stretch of amino acids that indicates where in the cell the polypeptide belongs |
| how a new polypeptide moves into an organelle | 1. signal sequence binds to a specific receptor protein 2. channel forms in organelle membrane 3. targeted protein moves in |
| 3 modifications performed on proteins after translation: | 1. proteolysis 2. glycosylation 3. phosphorylation |
| proteolysis | cutting of a polypeptide chain by proteases |
| glycosylation | addition of carbohydrates to proteins to form glycoproteins |
| phosphorylation | the addition of phosphate groups to proteins and is catalyzed by protein kinases |
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