Gene Expression
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| 6062834601 | How does DNA code for traits? | the DNA inherited by an organism dictates the synthesis of proteins which are the link between genotype and phenotype. |  | 0 |
| 6062834602 | Gene Expression | the process by which DNA directs protein synthesis, includes two stages: transcription and translation |  | 1 |
| 6062839605 | 1902 Archibold Garrod | "One Gene - One Enzyme" - first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions - He thought symptoms of an inherited disease reflect an inability to synthesize a certain enzyme example: alkaptonuria |  | 2 |
| 6062863082 | Revision: One Gene - One Protein | - some proteins are not enzymes (example: keratin in animal hair) - many proteins are composed of several polypeptides, each of which has its own gene (example: hemoglobin in blood - made of two polypeptides each coded its own gene) now: "One Gene - One Polypeptide" | 3 | |
| 6062879580 | Basic Principles of Transcription and Translation | - DNA provides the instructions to make a specific protein - RNA is the link between gene and protein - DNA codes for RNA and RNA codes for the protein |  | 4 |
| 6062895502 | Basics of Transcription & Translation cont'd | RNA is chemically similar to DNA, but RNA has a ribose sugar and the base uracil (U) rather than thymine (T) - RNA is usually single-stranded - RNA can leave the nucleus - getting from DNA to protein requires two stages: Transcription and Translation | 5 | |
| 6062906672 | Transcription | synthesis of RNA using information in DNA - site of Transcription: nucleus - end Product: messenger RNA (mRNA) - DNA: C A T G A C - RNA: G U A C U G |  | 6 |
| 6062914524 | Translation | synthesis of a polypeptide, using the information in the mRNA - site of translation: ribosomes - product: polypeptide (protein) |  | 7 |
| 6062938414 | Genetic Code | sequence of DNA bases that describe which Amino Acid to place in what order in a polypeptide - the genetic code gives the primary protein structure |  | 8 |
| 6062959873 | Codons: Triplets of Nucleotides | problem: RNA consists of four "letters" A, U, G, and C proteins consist of 20 "letters" - the amino acids - if 1 base = 1 amino acid, then 4 bases = 4 amino acids - we know there are 20! - Triplet Code: a series of three-nucleotide "words" that code for a specific amino acid - these "words" are then translated into a chain of amino acids - forming a polypeptide example: GGU = Glycine |  | 9 |
| 6062972551 | Genetic Code & Codons | genetic code is based on codons Codon: non-overlapping mRNA base triplets that code for a specific amino acid - 64 possible codons known - has redundancy; some AA's have more than 1 code - however: each 3 letter code codes for only 1 specific amino acid |  | 10 |
| 6063014817 | How many codons does it take to make 3 amino acids? | 3 codons | 11 | |
| 6063014818 | How many nucleotides does it take to make 5 amino acids? | 15 nucleotides | 12 | |
| 6063017187 | How many amino acids are made by 6 codons? | 6 amino acids | 13 | |
| 6063017188 | How many amino acids are made by 9 nucleotides? | 3 amino acids | 14 | |
| 6074446467 | RNA Polymerase | pries DNA strands apart and joins together the RNA nucleotides - assembles RNA nucleotides in the 5' -> 3' direction, using the DNA strand as a template - can start without a primer DNA Template: T A C G A T mRNA: A U G C U A |  | 15 |
| 6074469531 | Promoter | sequence signaling the end of transcription in bacteria | 16 | |
| 6074468429 | Terminator | DNA sequence where RNA polymerase attaches to begin RNA synthesis | 17 | |
| 6074471553 | Transcription Unit | entire stretch of DNA that is transcribed into mRNA |  | 18 |
| 6074482092 | 3 Stages of Transcription: Initiation | 1. Transcription Factors: proteins that assist the binding of RNA polymerase to initiate transcription - recognize TATA box 2. Transcription Initiation Complex: completed assembly of transcription factors and RNA polymerase II bound to a promoter |  | 19 |
| 6074512522 | 3 Stages of Transcription | Initiation: after the Transcription Initiation Complex is formed, RNA Polymerase unwinds and unzips DNA to start RNA synthesis Elongation: the polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5' -> 3' - in the wake of transcription, the DNA strands re-form a double helix Termination: stops when RNA Pol II reaches the polyadenylation signal sequence (AAUAAA) - the RNA transcript is released, and the polymerase detaches from the DNA after closing the helix |  | 20 |
| 6074523856 | Transcription Final Product | Eukaryotes: Pre-mRNA - this is a "raw" RNA that will need further processing Prokaryotes: do not need any processing | 21 | |
| 6074537575 | Eukaryotic Cells Modify RNA After Transcription | - in Prokaryotes, mRNA is directly translated into the polypeptide (protein) - in Eukaryotes, mRNA is processed first before being sent out into the cytoplasm these modifications make the mRNA molecule ready for translation |  | 22 |
| 6074565235 | RNA Processing | modification of pre-mRNA - during RNA processing both ends of the primary transcript (mRNA) are altered |  | 23 |
| 6074556046 | Alteration of mRNA Ends | 5' end: receives a modified G nucleotide "5' cap" 3' end: gets a poly-A tail - repeated A sequence function: prevent mRNA degradation by hydrolytic enzymes - helps attach to the ribosome during translation - helps facilitate export of the mRNA from the nucleus | 24 | |
| 6074577900 | RNA Splicing | removes noncoding (non-translating) regions of mRNA (introns) and joins together coding regions (exons) - this creates an mRNA strand that has a continuous coding sequence |  | 25 |
| 6074586071 | Introns | noncoding regions of mRNA that lie between exons |  | 26 |
| 6074588663 | Exons | coding regions that are translated into amino acid sequences |  | 27 |
| 6074595048 | Spliceosome | large complex of proteins and small RNAs - the spliceosome binds to several short nucleotide sequences along the intron - intron is released and the spliceosome joins together the two exons on either side |  | 28 |
| 6074613091 | Ribozymes | RNA molecules that act as enzymes - are sometimes Intron RNA and cause splicing without a spliceosome - in other words, can splice themselves out of the mRNA transcript! | 29 | |
| 6124282451 | Translation is the RNA- directed synthesis of a polypeptide | - genetic information flows from mRNA to protein through the process of translation - overall goal: use mRNA generated from transcription and form a polypeptide! | 30 | |
| 6124291884 | Transfer RNA (tRNA) | molecule that reads mRNA codons and builds a polypeptide accordingly - tRNAs transfer corresponding amino acids to the growing polypeptide in a ribosome - a tRNA molecule consists of a single RNA strand that is only 80 nucleotides long - 3' end of tRNA carries an amino acid - the other end of tRNA molecules contain an anticodon that pairs with the codon on the mRNA strand |  | 31 |
| 6124339583 | Accurate Translation Requires Two Steps: | 1st: a correct match between a tRNA and an amino acid - done by the enzyme aminoacyl-tRNA synthetase - 20 different synthetases! Uses ATP. 2nd: a correct match between the tRNA anticodon and mRNA codon | 32 | |
| 6124361037 | Ribosomes | - facilitate specific coupling of tRNA anticodons with mRNA codons during protein synthesis - large and small ribosomal units are made of proteins and ribosomal RNAs (rRNAs) - only join to form a ribosome when attached to an mRNA molecule |  | 33 |
| 6124387264 | Ribosome: 3 Binding Sites | 1. P site: holds the tRNA that carries the growing polypeptide chain 2. A site: holds the tRNA that carries the next amino acid to be added to the chain 3. E site: "exit" site, where discharged tRNAs leave the ribosome |  | 34 |
| 6124398428 | Building a Polypeptide | the three stages of translation require protein "factors" and ATP that aid in the translation process 1. Initiation 2. Elongation 3. Termination | 35 | |
| 6124422397 | Ribosome Association and Initiation of Translation | - initiation: brings together mRNA, tRNA (carrying 1st amino acid) and the two subunits of a ribosome - a small ribosomal subunit binds with mRNA and a special initiator tRNA carrying the a.a. Methionine to pair with mRNA "start" codon AUG - in eukaryotes, initiator tRNA binds to 5' Cap then scans downstream until reaching AUG - next a large ribosomal subunit arrives and forms "translation initiation complex" - requires energy and initiation factors |  | 36 |
| 6124440360 | Elongation of the Polypeptide Chain | - elongation: amino acids are added one by one to the previous amino acid at the C-terminus (COOH) of the growing chain - occurs in three steps: codon recognition, peptide bond formation and translocation - translation proceeds along mRNA in the 5' -> 3' direction |  | 37 |
| 6124485158 | Termination of Translation | - termination: Occurs when a stop codon in the mRNA reaches the A site of the ribosome - the A site accepts a protein called a release factor - the release factor adds a water instead of an amino acid - releasing the polypeptide (hydrolysis) - the translation assembly comes apart Stop Codons: UAG, UAA, and UGA - do not code for an amino acid |  | 38 |
| 6124517374 | Targeting Polypeptides to Specific Locations | -after translation, polypeptides fold to assume their specific conformation and are sometimes modified further - the destination of a protein is determined by the sequence of about 20 amino acids at the leading end of a polypeptide chain called the signal peptide - the signal peptide serves as a cellular zip code - directing proteins to their final destination |  | 39 |
| 6124532743 | Polyribosomes - Proks AND Euks | - cluster of ribosomes all reading the same mRNA - another way to make multiple copies of a protein simultaneously |  | 40 |
| 6156986445 | Mutations | changes in the genetic material of a cell - may be at a chromosome or DNA level | 41 | |
| 6156986446 | Point Mutations | chemical changes in one or a few nucleotide pairs of a gene - effects: none to fatal - Substitutions, Insertions and Deletions - the change of just one nucleotide in a DNA template strand can lead to the production of an abnormal protein |  | 42 |
| 6157003103 | Nucleotide-Pair Substitution | replaces one nucleotide and its partner with another pair of nucleotides |  | 43 |
| 6157004588 | Silent Mutations | have no effect on the amino acid produced by a codon because of the redundancy in the genetic code |  | 44 |
| 6157021741 | Missense Mutation | still codes for an amino acid, but not the correct one - most common |  | 45 |
| 6157037752 | Nonsense Mutation | change in amino acid codon into a premature stop codon - nearly always leading to a nonfunctional protein |  | 46 |
| 6157051216 | Insertions and Deletions | additions or losses of nucleotide pairs in a gene - NOT in multiples of three - can have disastrous effects on the resulting protein!!! - may produce a frameshift mutation (example: Tay Sach's) - alters the reading frame of the genetic message |  | 47 |
| 6157095937 | Mutagens | materials that cause DNA changes 1. Radiation (example: UV light, X-rays) 2. Chemicals (example: 5-bromouracil) - any material that can chemically bond to DNA or is chemically similar to Nitrogen bases will be a strong mutagen |  | 48 |
| 6157105032 | What is a gene? | a gene is a region of DNA that can be expressed to produce a final functional product - the product can be a protein or a RNA molecule | 49 |
