CHapter 17 From Gene to Protein
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71 terms
Terms | Definitions |
|---|---|
 deoxyribose | the molecule that is used to determine the polarity of the DNA strand |
| primase | the enzyme that adds ribonucleotibes to start the synthesis of a new DNA strand |
| deoxyribose | the molecule that is used to determine the polarity of the DNA strand (it is negative) |
| primase | the enzyme that adds ribonucleotides to start the synthesis of a new DNA strand |
| Beadle and Tatum | exposed bread mold to x-rays which created mutants that were unable to synthesize certain molecules; they developed the one gene-one enzyme hypothesis |
| one gene-one enzyme hypothesis | states that each gene dictates production of a specific enzyme |
| proteins | the link between genotype and phenotype |
| one gene-one polypeptide hypothesis | the one gene-one enzyme hypothesis was revised because not all proteins are enzymes |
| RNA | the intermediate between genes and proteins; contain ribose instead of deoxyribose, are typically single stranded, and use uracil nucleotides instead of thymine nucleotides; elongates 5-3 |
| transcription | the synthesis of RNA under the direction of DNA; it produces messenger RNA; occurs in the nucleus; only one of the 2 strands of dna is transcribed |
| mRNA | messenger RNA; carries a genetic message from the DNA to the protein-synthesizing (translation) machinery of the cell, read from 5-3 |
| translation | the synthesis of a polypeptide, which occurs under the direction of mRNA; occurs in the cytoplasm |
| ribosome | the sites of translation; they faciliate specific coupling of tRNA and anticodons with mRNA codons in protein synthesis |
| polypeptide | a polymer of amino acids linked together by peptide bonds |
| RNA synthesis vs DNA synthesis | 1) differs in substrates 2) the entire genome is not transcirbed; only specific genes, a type of regulation that requires regulatory units |
| primary transcript | pre-mRNA; the initial RNA transcript from any gene |
| promoter | the DNA sequence to which RNA polymerase attaches and initiates transcription |
| RNA polymerase | moves along the DNA and untwists the two strands and joins the RNA nucleotides as they base-pair along the DNA; assemble a polynucleotide only in the 5 to 3 primed direction like DNA polyermase but they don't need a primer (can start from scratch); a gene can be trancribed at the same time by several RNA polymerases |
| terminator | the sequence that signals the end of transcription |
| transcription unit | the stretch of DNA that is transcribed into an RNA molecule |
| TATA box | a DNA sequence that is required for initiating RNA synthesis |
| polyadenylation signal | a stretch of RNA where all the bases are adenines; at the end of an RNA molecule, it is a sequence that signals termination in eukaryotic mRNA (AAUAAA) |
| RNA polymerase II | the enzyme that synthesizes mRNA; transcribes a sequence on the DNA called polyadenylation signal sequence; adds nucleotides to the 3- end of the growing rna molecule |
| transcription factors | a collection of proteins the mediate the binding of RNA polymerase and the initation of transcription |
| RNA processing | enzymes in the eukaryotic nucleus modify the pre-mRNA before the genetic messages are dispatched to the cytoplasm; both ends of the primary transcript are altered; usually some interior parts of the RNA are cut out and remaing parts are spliced together |
| RNA splicing | removes introns and joins exons, creating mRNA with a continuous coding sequence |
| poly A tail | when the pre-mRNA is modified, this is formed at the 3 primed end of the mRNA; its is a combination of 50-250 adenine nucleotides |
| 5 cap | when pre-mRNA is modified the 5 primed end is synthesized first; it is a modified form of a guanine nucleotide |
| exon | the coding regions of mRNA; are eventually expressed, usually translated into amino acid sequences |
| intron | most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions called these |
| spliceosome | RNA splicing is carried out by this in some cases; they consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites; interacts with certain sites along the intron, releasing the introns and combining the exons |
| alternative RNA splicing | some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing; because of this, the number of different proteins an organism can produce is much greater that its number of genes |
| adenine | the base uracil in RNA binds to this base in the template of DNA |
| ribozyme | catalytic RNA molecules that function as enzymes and can splice RNA; the discovery of this rendered obsolete that the idea that biological catalysts are proteins |
| 3 RNA properties that enable it to function as an enzyme | 1) it can form 3D structure because of its ability to base pair with itself 2) some bases in RNA contain functional groups 3) RNA may hydrogen bond with other nucleic acid molecules |
| transcription-review | 1) has uracil 2) 2primed hydroxyl group that makes it unstable 3) synthesized in 5 to 3 primed direction 4) single stranded 5) can be edited 6) can have catalytic activity |
| triplet code | the flow of information from gene to protein is based on this; a series of nonoverlapping, three nucleotide words; smallest units of uniform length that can code for all the amino acids |
| template strand | the one of the two DNA strands that are synthesized during transcription |
| codon | mRNA base triplets |
| reading frame | codons must be read in the correct groupings in order for the specified polypeptied to be produced; in the correct this |
| genetic code | nearly universal, shared by the simplest bacteria to the most complex animals therefore genes can be transcribed and translated after being transplanted from one species to another |
| tRNA | a cell translates an mRNA message into protein with the help of this; transfer RNA; 1) carries a specific amino acid on one end 2) has an anticodone on the other end 3) consists of a single RNA strand that is about 80 nucleotides |
| anticodon | at the opposing end of tRNA (opposing the amino acid); it base-pairs with a complementary codon on mRNA |
| snRNP | small nuclear ribonucleoproteins; recognize the splice sites in the pre-mRNA; located in the nucleus and are composed of proteins and RNA |
| snRNA | the RNA in a snRNP that is about 150 nucleotides long |
| aminoacyl-tRNA synthetase | first step of translation; this correctly matches tRNA and an amino acid; there are only 20 different types of this enzyme, one for each AA; it catalyzes the covalent attachment of the AA to its tRNA by the hydrolysis of ATP |
| wobble | flexible pairing at the third base of a codon which allows some tRNAs to bind to more than one codon |
| rRNA | ribosomal RNA; the two ribosomal units (large and small) are made of proteins and this |
| p site | holds the tRNA that carries the growing polypeptide chain |
| a site | holds the tRNA that carries the next amino acid to be added to the chain |
| e site | the exit site where discharged tRNAs leave the ribosome |
| 3 stages of translation | initiation, elongation, termination; all require protein factors that aid in this process |
| AUG | the start codon; also translates for methionine |
| water | the molecule that is added instead of an AA to terminate translation |
| polysome | a number of ribosomes can translate a single mRNA simultaneously forming this; a string of ribosomes; allows for the copies of a polypeptide very quickly |
| mutation | changes to the genetic information of a cell (or virus) |
| point mutation | chemical changes in just one base pair of a gene; the change of a single nucleotide in a DNA template strand can lead to the production of an abnormal protein; two types: base-pair substitutions and insertions/deletions |
| base pair substitution | the replacement of one nucleotide and its partner with another pair of nucleotides |
| base pair insertion | addition of nucleotide pairs in a gene; have the most major effect on the resulting protein |
| base pair deletion | loss of nucleotide pairs in a gene; have the most major effect on the resulting protein |
| silent mutation | type of base pair substitution; has no effect on the AA produced by a codon because of redundancy in the genetic code |
| missense mutation | type of base-pair substitution; still codes for an AA but not necessarily the right AA |
| nonsense mutation | type of base-pair substitution; changes an AA codon into a stop codon and nearly always leads to a nonfunctional protein |
| frameshift mutation | insertion or deletion of nucleotides that alter the reading frame; unless the frameshift is near the end of the gene, the protein is almost certainly nonfunctional |
| mutagen | physical or chemical agents that can cause mutations |
| functions of poly A tail and 5 cap | 1) facilitate the export of mRNA 2) protect mRNA from hydrolytic enzymes 3) help ribosomes attach to the 5 end once the mRNA is in the cytoplasm |
| initiation of translation | brings together mRNA, a tRNA with the first AA, and the two ribosomal subunits; 1) a small ribosomal unit binds with mRNA and a special initiator tRNA 2) the small subunit moves along the mRNA until it reaches the start codon 3) proteins (initiation factors) bring the large subunit of the ribosome to complete the complex |
| termination of translation | occurs when a stop codon in the mRNA reaches the A site of the ribosome; 1) the A site accepts a protein called a release factor 2) the release factor causes the addition of a water molecule instead of an AA 3) this releases the polypeptide |
| initiation factors | proteins that bring in the large subunit that completes the translation initaion complex |
| T4 protein and T4 DNA | a bacterium is infected with an experimentally constructed phage composed of T2 phage protein coat and T4 phage DNA. The new phage would produce this |
| UTR | untranslated regions at the 5 and 3 primed ends; are part of the mRNA that will not be translated into protein but promote ribosome binding |
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