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MCAT Bio. Chem Ch. 7
| Question | Answer |
|---|---|
| Central Dogma of Replication | DNA --> RNA --> Proteins |
| Degenerate code allows: | Multiple codons to encode for the same amino acid. |
| Initiation Codon (Start Codon) | AUD |
| 3 Termination Codons (Stop Codons) | UGA, UAA, UAG |
| Redundancy and wobble (third base in codon): | Allows mutations to occur without effects in the protein. |
| Silent Mutations | Have no effect on protein synthesis |
| Nonsense (Truncation) Mutation | Produce a premature stop codon |
| Missense Mutations | Produce a codon that codes for a different amino acid |
| Frameshift Mutation | Result from nucleotide addition or deletion and change the reading frame of subsequent codons |
| RNA Is Structurally Similar To DNA Except: | Substitution of a ribose sugar for Deoxyribose. Substitution of Uracil for Thymine. It is single-stranded instead of double-stranded. |
| Messenger RNA (mRNA) | Carries the message from DNA in the nucleus via transcription of the gene, travels into the cytoplasm to be translated. |
| Transfer RNA (tRNA) | Brings in amino acids, recognizes the codon on the mRNA using its anticodon. |
| Ribosomal RNA (rRNA) | Makes up the ribosome, enzymatically active. |
| Helicase And Topoisomerase: | Unwind the DNA double helix |
| RNA Polymerase II | Binds to the TATA box within the promoter region of the gene (25 base pairs upstream from first transcribed base) |
| hnRNA | Synthesized from the DNA template (antisense) strand |
| Posttranscriptional Modifications Include | A 7-methylguanylate triphosphate cap is added to the 5' end. A polyadenosyl (poly-A) tail is added to the 3' end. |
| Spliceosome | Location where splicing is done by snRNA and snRNP's |
| Introns Are Removed In A: | Lariat structure |
| Exons Are: | Ligated together |
| Polycistronic Genes | Genes in which prokaryotic cells can increase the variability of gene products from one transcript (starting transcription in different sites within the gene leads to different gene products) |
| Alternative Splicing | Method in which eukaryotic cells can increase variability of gene products |
| tRNA | Translates the codon into the correct amino acid |
| Ribosomes | Factories where translation or protein synthesis occurs |
| Initiation (First Stage Of Translation) | Occurs when the 30S ribosome attaches to the Shine-Dalgarno sequence and scans for a start codon. It lays down N-formylmethionine in the P site of the ribosome. |
| Elongation | Involves the addition of new aminoacyl-tRNA into the A site of the ribosome and transfer of the growing polypeptide chain from the tRNA in the P site to the tRNA in the A site. The now uncharged tRNA pauses in the E site before exiting the ribosome. |
| Termination | Occurs when the codon in the A site is a stop-codon. Release factor places a water molecule on the polypeptide chain and thus releases the protein. |
| Initiation, Elongation, And Release Factors | Help with each step in recruitment and assembly/disassembly of the ribosome. |
| Posttranslational Modifications Include: | Folding by chaperones. Formation of quaternary structure. Cleavage of proteins or signal sequences. Covalent addition of other biomolecules (phosphorylation, carboxylation, glycosylation, prenylation). |
| Jacob-Monod Model Of Repressors And Activators | Explains how operons work |
| Operons | Inducible or repressible clusters of genes transcribed as a single mRNA. |
| Inducible Systems (ex: lac operon) | Bound by a repressor under normal conditions. They can be turned on by an inducer pulling the repressor from the operator site. |
| Repressible Systems (ex: trp operon) | Transcribed under normal conditions. They can be turned off by a corepressor coupling with the repressor and the binding of this complex to the operator site. |
| Transcription Factors | Search for promoter and enhancer regions in the DNA |
| Promoters | Are within 25 base pairs of the transcription start site |
| Enhancers | Are more than 25 base pairs away from the transcription start site |
| Modification Of Chromatin Structure: | Affects the ability of transcriptional enzymes to access the DNA through histone acetylation (increases accessibility) or DNA methylation (decreases accessibility) |
Created by:
SamB91
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