Protein Synthesis DNA 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 RNA RNA 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 Thymine Types 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 Mutations If 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 Mutations 1 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 GGG 2 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 worse 3
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