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DNA AND PROTEIN SYSNTHESIS DNA PROTEIN What structures are found in the nucleus? What is a gene? • Gene: a portion of DNA that contains the codes (instructions) for one protein. GENE • A gene is a sequence of nucleotides that has the code (instructions) for making a specific protein • The average gene is 3000 bases • Total number of genes is 30,000 to 35,000 Protein Synthesis The building of proteins from amino acids • Why are proteins important? – Make up important structures like muscles and cell membranes. – Substances like enzymes, antibodies and hormones are made of proteins – Traits like hair and eye color are the results of proteins RIBOSOME Where is DNA? Where are proteins made? ribosome • Where are proteins synthesized ? By the ribosomes In the cytoplasm. • What are proteins made of? – Proteins are long chains of amino acids – There are 20 different amino acids • The instructions for making proteins (the order of the amino acids in a particular protein) are encoded in the DNA (the code) CODON • Codon – a set of three nitrogenous bases that represents an amino acid Codon • The bases are arranged in threes called codons. AGG-CTC-AAG-TCC-TAG TCC-GAG-TTC-AGG-ATC Protein Synthesis takes place in 2 stages transcription translation • RNA RNA – Ribonucleic acid – RNA is similar to DNA but is single stranded – RNA contains the sugar ribose (not deoxyribose) – The nitrogen base uracil replaces thymine Three Types of RNA • Messenger RNA (mRNA) – Is formed in the nucleus – Carries the instructions from the DNA in the nucleus to the ribosomes in the cytoplasm –“The Messenger” CODON • Order of nitrogen bases in mRNA that determines the type and order of amino acids in a protein • mRNA has the CODON! • There are 64 possible codons, but only 20 amino acids to code for TRANSFER RNA • Transfer RNA (tRNA) – Carries amino acids from the cytoplasm to the ribosome. –Has the anticodon – “The Worker” RIBOSOMAL RNA (rRNA) – The ribosome is made of rRNA. Transcription • During the production of proteins the “blueprints” (instructions) are located in the nucleus, in a code in the DNA • DNA acts as a template for making messenger RNA Complementary base pairing DNA Base Complementary RNA Base G C C G A U T A Transcription • mRna picks up the triplet code from the DNA • m RNA leaves the nucleus. •The instructions (codon) are then carried to the cytoplasm • A ribosome attaches to the mRNA. • The instructions carried by the mRNA will be used to assemble the amino acids in the proper order Translation • The amino acids are brought to the ribosomes by the tRNA molecules to be assembled into a protein (translation) • The order of the amino acids is determined by the codon on the mRNA Protein Synthesis • The tRNA anticodon pairs with the mRNA codon • The tRNA releases the amino acid which bonds to the other AA ‘s forming a chain = protein MUTATIONS Mutations • If DNA is not copied exactly, proteins made from its instructions could be made INCORRECTLY • Mutation: any permanent change in the DNA sequence in a gene or chromosome. • Factors that cause mutations: X rays, sunlight, and some chemicals Results of a Mutation • Genes control the traits you inherit. • Without correctly coded proteins, an organism can’t grow, repair, or maintain itself. • A change in a gene or chromosome can change the traits of an organism. Results of a Mutation • If the mutation occurs in a body cell, it might not be life threatening to the organism. • If a mutation occurs in a sex cell, then all the cells that are formed from that sex cell will have that mutation. Results of a Mutation • Many mutations are harmful to organisms, often causing their death. • Some mutations do not have any effect on the organism. •Some mutations can be helpful and give the organism a better chance of surviving. DNA and Mutations – Lets looks at different mutations THE DOG BIT THE CAT Mutations - Substitution THE DOG BIT THE CAT • Substitution - Replace just one letter: THE DOG BIT THE CAR Deletion THE DOG BIT THE CAT • Deletion: Delete just one letter (T): THE DOG BIT HEC AT Insertions THE DOG BIT THE CAT • Insertion - Add just one letter (E): THE DOE GBI TTH ECA T Cells have “proof reading” proteins that constantly check the DNA and fix errors, so most are corrected