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UNC-Chapel Hill BIOL 101 - Chapter 17- Protein Synthesis _ Mutations

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Protein SynthesisDNA code for the production of proteins (including enzymes). Proteins are made of subunits Amino Acids. There are 20 essential amino acids (chart).DNA can’t leave the nucleus, but the code must be taken to the ribosomes where proteins are made. Another nucleic acid helps with this process: RNARNA has similarities and differences with DNA:● Made of nucleotides (sugar, phosphate, base)● Sugar is ribose● Single-stranded● Has the Adenine, Cytosine, and Guanine, but no Thymine. Has Uracil, which is similar to ThymineTypes of RNA:1. messenger RNA (mRNA) reads the DNA code in a process called Transcription.2. transfer RNA (tRNA) has a code to match the mRNA code. Brings amino acids to the ribosome to assemble a protein in a process called Translation.3. ribosomal RNA (rRNA) helps to assemble the ribosome complex during protein synthesis.Steps to Make a Protein:1. Transcription takes place in the nucleus. The mRNA reads the DNA code matching bases as A-U, C-G.2. Translation: mRNA leaves the nucleus and goes to a ribosome. tRNA match the mRNA code A-U, C-G. Each tRNA carries with it an amino acid. Amino acids are assembled in chains to form proteins.The DNA code is read in groups of three bases called codons. With four different bases read in groups of three, there are enough codes to code for the twenty amino acids, with codons to spare.● Chart: Each amino acid has several possible codons. This helps in case of mutations. If a codon does change, there is still a chance to get the same amino acid.● But for any particular codon, there is only ONE amino acid.DNA & MutationsIf there is a change in the DNA code, the mRNA code would be changed and this could result in a change in the resulting protein. A change in the DNA code is called a Mutation.The majority of mutations are not life threatening. Some mutations are life threatening and called Lethal.Mutations can be spontaneous (no clue why it happened) or induced... by chemicals and environmental exposure (formaldehyde, tobacco products, radiation, benzene, oil products).Types of Mutations1. Substitutions: Base pair substitution is the replacement of one base pair with another. Depending on the location of the change, there might be little or no change to the protein.○ The change might give a codon that codes for the original protein○ The “new” protein could have similar properties of the original protein.○ The mutation could be beneficial, as with Morgan Horse.○ Missense mutations produce a different amino acid○ Nonsense mutations produce stop codons and usually lead to non-functional proteins○ CTG GAG → CTG GGG2. Insertions or Deletions are more serious. Usually have greater negative effect on proteins than substitutions.○ Base Pair Insertion: the insertion of one or more base pairs○ CAT CAT CAT__CAT CAT → CAT CAT CAT ACA TCA○ Base Pair Deletion: the loss of one or more base pairs○ CAT CAT CAT CAT CAT → CAT CAT CAT C__TC ATC○ mRNA reads the DNA code as triplet codons, adding or deleting a base pair can cause a “frameshift” in how the codons are read. If the insertion or deletion is three base pairs, the change might not be harmful.○ If the mutation occurs at the end of a protein, the resulting protein might still be functional. Mistakes at the beginning of a protein are much


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UNC-Chapel Hill BIOL 101 - Chapter 17- Protein Synthesis _ Mutations

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