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Genetic Codes

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Course Code
BLG 312
Franklyn Prescod

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Genetic Code  DNA codes for assembly of amino acids / forms a polypeptide chain (proteins - enzymes)  The code is read in a sequence of three bases called o Triplets on DNA (e.g. CAC TCA) o Codons on mRNA (e.g. GUG AGU) o Anticodons on tRNA (e.g. CAC UCA) - must be complementary to the codon of mRNA  Each triplet codes for one amino acid  Single amino acid may have up to 6 different triplets for it due to the redundancy of the code / some amino acids are coded by more than one codon (degenerate code)  Same triplet code will give the same amino acid in all organisms (universal code)  We have 64 possible combinations of the 4 bases in triplets, 43  No base of one triplet contributes to part of the code next to it (non-overlapping)  Few triplets code for START and STOP sequences for polypeptide chain formation o START: AUG o STOP: UAA, UAG, UGA DNA and Inheritance  Cell metabolism: reactions inside cells  Metabolic pathway: sequence of chemical reactions  Alleles: different forms of the same gene  Gene: length of DNA that carries the code for a protein (enzyme) o Enzyme effect the cell's metabolism o Visible changes are described with the phenotype o The phenotype is influenced by the metabolic pathway  Therefore o DNA controls enzyme production o Enzymes control metabolic pathways o Metabolic pathways influence the phenotype of an organism Alleles and Genes  Humans have 46 chromosomes o 22 of them are paired up as homologous chromosomes o Females have an additional homologous pair of sex chromosomes (XX) o Males have an X and Y sex chromosome  Pair of homologous chromosomes o One of the pair is inherited from the mother, one from the father o Gene is a small section of DNA that codes for a specific characteristic  Hair colour,  Eye colour, ... o Found
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