Protein Synthesis DNA RNA Protein

How is the code in DNA Used to Make Proteins? Using RNA (Ribonucleic Acid)! RNA is similar to DNA (they are both nucleic acids, and both are made up of nucleotides) but RNA has 3 significant differences: It is Single stranded (instead of double stranded like DNA) It has the sugar ribose (instead of deoxyribose like DNA) It contains the base Uracil (U) instead of Thymine

3 Types of RNA mRNA is Messenger RNA – made from a section of DNA (a gene) in the nucleus (carries DNA’s “message”) tRNA is transfer RNA – responsible for transferring amino acids to a ribosome to make a protein in the cytoplasm rRNA isRibosomal RNA – makes up ribosomes that help assemble proteins

Transcription: an mRNA COPY of a DNA section (gene) is made in the nucleus DNA mRNA Enzymes “unzip” a section of DNA Complementary RNA nucleotides pair with DNA nucleotides and bond together (AUCG) to make a SINGLE strand of mRNA based on the DNA code The mRNA strand breaks away from the DNA and takes the DNA “message” from the nucleus to the cytoplasm

DNA mRNA = Transcription Enzymes “read” the DNA bases in a gene and put together a complementary, single-stranded mRNA molecule based on the DNA code Example: DNA sequence: TAC CCA TGC CTG mRNA sequence: AUG GGU ACG GAC Remember, NO THYMINE in RNA!

Translation: the code in mRNA is TRANSLATED into a sequence of amino acids – a protein mRNA travels out of the nucleus to a ribosome in the cytoplasm The ribosome holds the mRNA in place tRNA brings amino acids to the ribosome The nucleotides on mRNA are divided into groups of 3 (“triplets”) Each set of 3 nucleotides on mRNA is called a CODON One codon is the “code” for one amino acid Codons on mRNA match up with anticodons on tRNA for specific amino acids Each tRNA delivers one amino acid The amino acids are attached (bonded) together to make a protein (they are attached together based on the original sequence in the DNA molecule that mRNA was made from!) RNA Protein

Codons and Anticodons Codon - a group of 3 bases in mRNA (that “code” for ONE amino acid) *There are 20 different amino acids Anticodon – a group of 3 bases in tRNA (that are complementary to a codon in mRNA)

“Decoding” the message – the Genetic Code (based on codons in mRNA) How do mRNA, tRNA and the ribosomes know which amino acids to put into the protein? THE GENETIC CODE! Based on codons (triplets) in mRNA Universal to ALL LIFE!!! http://img.genciencia.com/2007/06/codigogenetico2.gif

Transcription and Translation http://www.youtube.com/watch?v=41_Ne5mS2ls&NR=1&safety_mode=true&persist_safety_mode=1&safe=active

The Protein Each protein is a chain of amino acids that has a specific job The structure (shape) of the protein depends on the sequence of amino acids and the folding of the protein

Transcribe and Translate! DNA: TAC ACT GGC TAA CGT TCC AGT ACC AAT GCG ATT mRNA: ________________________________________ tRNA: _________________________________________ amino acids: _____________________________________ DNA: TAC ATC GTC TCG CCT AGT CCT GAA CTG CCA ACT mRNA: _________________________________________ tRNA: __________________________________________

Mutations Mutation = a change in DNA (genetic material) Mutations can change ONE single base pair (point mutations) or they can change long sequences of DNA/ chromosomes IF mutations occur in gametes, they can be passed on to offspring! IF the bases in DNA are changed, the mutation is copied into mRNA during transcription, and then put into the amino acids/ protein during translation (this usually means the protein doesn’t “work” properly, if at all)

Mutations Original DNA: TAC CTT CAG GCG Original mRNA: AUG UGG GUC CGC Original Amino Acids: Met - Glu - Val - Arg Mutated DNA: TAC CAT CAG GCG Mutated mRNA: AUG UGA GUC CGC Mutated Amino Acids: Met – Val – Val - Arg Example: Sickle cell anemia (CTT in DNA is changed to CAT, changing one amino acid in the protein)- red blood cells are sickle- shaped instead of round and do not carry oxygen as well

Label the Diagram Nucleus DNA mRNA Transcription cytoplasm tRNA Ribosome Amino acid Protein Codon anticodon translation

Complete the Following Table DNA Sequence AAC TAG GGT Explain how DNA is transcribed. mRNA codons What does the ‘m’ mean in mRNA? Explain why. tRNA anti-codons Explain how the mRNA code is translated into amino acids. Amino acid sequence Describe how a protein is formed and identify 3 roles of proteins.