2Bellringer 11/4/10Based on the picture on the board, where does transcription occur?Where does translation occur?
3Section 2: Genes and Proteins The sequence of nucleotides in DNA contain information. This information is used to make proteinsProteins make cells and regulate their functions.Proteins are made of subunits/monomers called amino acidsThe sequence of DNA nucleotides determine the amino acids used to build proteins
4RNA-Ribonucleic Acid Full name: Ribonucleic Acid In base pairing, thymine (T) is replaced by uracilFunction: plays a role in making proteinsRNA Nucleotide Structure:Ribose (sugar)PhosphateNitrogen basesA pairs with UC pairs with G
5Types of RNAmRNA: messenger RNA; made from DNA & it carries DNA information from the nucleus to the cytoplasmrRNA: ribosomal RNA; combines with ribosomes to make proteinstRNA: transfer RNA; carries amino acids to the ribosomes
6Types of Bases/Base Pairs Comparing DNA and RNADNARNAStrands21SugarDeoxyriboseRiboseTypes of Bases/Base PairsA-TC-GDNA – RNA RNA-RNAA-U U-AC-G C-GSo why is RNA important? Because DNA is too big to leave the nucleus and it uses RNA to take its message out into the cytoplasm.
7Transcription Location: Nucleus Purpose: DNA information is copied into mRNA.Caused by RNA Polymerase (an enzyme)DNA is safe in the nucleusUses mRNATo send a message to the cytoplasm
8FYI: How does this happen? Unzip one gene in DNAMatch up bases to one side of gene in DNAA binds with U, C binds with G.mRNA detaches from the DNAmRNA moves out of the nucleus and into the cytoplasmDNA: GAG AAC TAG TACRNA: CUC UUG AUC AUG
9Translation Location: Cytoplasm at the Ribosomes Purpose: tRNA matches to the mRNA to make a specific amino acid chain which is a protein.
10How are the Nucleotides of Messenger RNA Translated into a Protein? Events of translation:The first three bases of mRNA (codon) join the ribosome. Its usually AUG – considered the start codon).tRNA brings the “amino acid” down to the ribosome. The three bases on tRNA (anticodon) match the complementary bases on mRNA.Each tRNA has an amino acid, which is determined by its anticodon. Ex: codon (AUG) is for the amino acid - methionineThe amino acids are joined by polypeptide bonds.The resulting chain of amino acids are called a PROTEIN.
11Codons & AnticodonsCODON: mRNA bases needed to call an amino acid to the ribosomeStart codon: AUG and it codes for the amino acid methionineStop codon: mRNA that means the end of the AA chain has been reachedANTICODON - segment of three bases on tRNA that is complementary to the mRNA codon.
13DNA DNA with DNA mRNA DNA with RNA mRNA with tRNA ProcessInformation for processProductType of Base Pairing RequiredReplication (synthesis of DNA)Entire length of double helixDNADNA with DNATranscription (synthesis of RNA)Small part of a DNA strandmRNADNA with RNATranslation (synthesis of protein)ProteinmRNA with tRNA
14But What Happens When Any of These Processes Goes Wrong…
15Mutations… What is a mutation? Any change in the DNA sequence What is a mutagen?Any agent that can cause a change in DNAHow can mutations happen?Spontaneous mistakes in base pairingsradiationchemicalshigh temperatures
16Types of MutationsPoint Mutation: a change in a single base (like a substitution)GAGCTC CUC LeucineCorrect DNA Correct mRNA Correct AAGCGCTC CGC ArginineA should pair with T, but instead C is mismatched to TPoint mutation mutated mRNA Wrong AA
19Frameshift mutation: when one or more bases are added or deleted from DNA. Correct DNA: ATA CCG TGATAT GGC ACTCorrect mRNA: UAU GGC ACUCorrect amino acids: Tyrosine Glycine ThreonineExtra inserted base SHIFTS how we read the codons (3 bases), which changes the amino acidsFrameshift mutation ATG ACC GTG Ain DNA: TAC TGG CAC TMutated mRNA: UAC UGG CAC UWrong amino acids: Tyrosine Tryptophan Histadine
22Chromosomal Mutations Structural changes in chromosomesCaused by four types of mistakes
23Insertion- When a part of a chromatid breaks off and is added to its sister chromatid so that the gene is duplicated
24Deletion- When a part of a chromosome is left out
25Translocation & Inversion Translocation: When a part of the chromosome breaks off and is added to a different chromosomeInversion: When a part of the chromosome breaks off and is reattached backwards
26MutationsFrameshift mutations can have catastrophic effects on genes because ALL the codons that follow the shift will be altered, not just one.Proofreading enzymes are able to repair some damages to DNA