Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # The order of nucleotide bases in a strand of DNA is the DNA sequence -instructions for the cell A sequence of 3 nucleotide bases (codon) is an instruction to add one particular amino acid, (from the twenty possible) at that location, to a protein chain Proteins are long chains of amino acids in a sequence determined by the sequence of codons in a gene DNA sequence Codon Amino acid protein

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # Characteristics Protein synthesis Transcription mRNA translation Proteins act as chemical messengers and cause characteristics: shapes, sizes, colors and textures of an organism Protein synthesis includes two steps: transcription of a gene into a strand of messenger RNA (mRNA) translation of an mRNA strand into a protein

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # Transcription: in the nucleus, helicase separates complementary base pairs on the two strands of a gene RNA polymerase attaches free RNA nucleotides to template strand DNA form a primary RNA transcript this transcript is modified to become the completed mRNA strand mRNA travels through a nuclear pore out to the cytoplasm Helicase RNA polymerase Primary RNA transcript mRNA cytoplasm

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # RiboNucleic Acid Ribose Uracil (U) Nucleus RNA stands for RiboNucleic Acid. RNA is made from DNA, but… RNA has a different type of sugar (ribose not deoxyribose) RNA is a single strand RNA has uracil (U) not thymine (T) DNA never leaves the nucleus

The DNA to RNA base-pairing rules are (DNA – RNA) A – U T -- A C – G Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # DNA to RNA base-pairing rules (NEW ONES!) mRNA tRNA rRNA The DNA to RNA base-pairing rules are (DNA – RNA) A – U T -- A C – G G – C Three types of RNA: Messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA)

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # Translation: In the cytoplasm, ribosomal subunits form around one end of the mRNA strand A tRNA with an anticodon complementary to the first mRNA codon bonds The next complementary tRNA attaches to the next mRNA codon and attaches its amino acid to the first amino acid Complementary tRNAs continue attaching their amino acids to the protein chain Ribosomal subunits tRNA anticodon protein

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # Mutation insertion deletion substitution translocation Mutations occur when there is a change in the order of bases in a DNA strand An insertion occurs when an extra nucleotide is added A deletion occurs when a nucleotide is deleted A substitution occurs when one nucleotide is replaced with a different nucleotide Translocation occurs when part of the DNA sequence moves to another location

Ch.6s.2 Genetics: Protein Synthesis First Last Date Period # Repair enzymes Fixed No change in protein Negative change Positive change mutagen Repair enzymes normally fix mutations if mutations are not fixed, 3 consequences could occur Changes in DNA may not cause any change in the protein (most common) Changes in DNA may cause a negative change in protein Changes in DNA may cause a positive change in protein A mutagen is anything that causes a mutation in DNA Radiation, chemicals