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08 transcription, translation and mutation
- 1. Transcription, Translation and Mutation • FromDNA to Protein (11.2) • Genetic Changes (11.3)
- 2. Answer these questions: Whatis coded for in DNA? How is it coded? What is the primary structure of a protein? Proteins The sequence of A, T, G, C Sequence of amino acids What are proteins used for? Structure Controlling the biochemistry of an organism Enzymes, antibodies
- 3. From DNA toProtein DNA cannot leave the nucleus Protein is made at the ribosomes in the cytoplasm and attached to the rough endoplasmic reticulum Therefore, a message must be sent from the DNA to the ribosome
- 4. From DNA toProtein The messenger is RNA (mRNA) DNA Protein: occurs in 2 steps Transcription Making the coded message (mRNA) Translation Reading the coded message
- 5. How is RNAdifferent from DNA? RNA DNA Single-stranded Double-stranded Sugar = ribose Sugar = deoxyribose A, U, G, C A, T, G C
- 7. 3 types ofRibonucleic Acid (RNA) mRNA rRNA Messenger RNA Brings instructions from DNA in the nucleus to the cytoplasm (where ribosomes are found) Ribosomal RNA Part of the ribosome that binds to the mRNA and uses the instructions to assemble the amino acids in the correct order tRNA Transfer RNA Delivers the amino acids to the ribosome to be assembled into a protein
- 8. Transcription: DNA tomRNA DNA is unzipped mRNA is formed, complementary to one of the strands of DNA 1. 2. RNA polymerase (enzyme) joins the nucleotides of RNA together
- 9. Transcription The mRNA isprocessed 3. Not all nucleotides in DNA code for making protein Introns – noncoding sequences Exons– coding sequences Introns are removed and exonsare spliced together For protection from enzymes in the cytoplasm, the ends of the RNA strand are ‘covered’ 5’ GTP cap 3’ poly-A tail
- 10. Translation: mRNA toProtein ~20 amino acids and 4 nitrogenous bases (A, U, G, C) How can 4 bases form a code for all possible proteins? A group of 3 bases code for 1 amino acid Each group is called a codon 64 combinations are possible when a sequence of 3 bases is used, therefore there are 64 different mRNA codons Not all codons code for proteins. UAA = stop AUG = start More than one codon can code for the same amino acid, but for any one codon, there can only be one amino acid
- 13. Translation: mRNA toProtein
- 14. Mutations Answer this question: Howdoes DNA encode the characteristics of an organism? Each codon in DNA codes for an amino acid (or start/stop) used to build protein which shapes an organism's characteristics DNA mRNA Protein Characteristics A mutation is any change in the genetic code (nucleotide sequence) Mutations are random
- 15. The Causes ofMutations DNA fails to copy accurately External influences can create mutations Chemicals or radiation break down DNA When the cell repairs the DNA, it might not do a perfect job of the repair
- 16. Types of Mutations Substitution Onebase is exchanged for another This will change the codon which could… Code for a different amino acid and change the protein Code for the same amino acid and do nothing (silent mutation) Change the code to ‘stop’ and make an incomplete protein that will probably not function Insertion Extra base pairs are inserted into a new place in the DNA
- 17. Types of Mutations Deletion Asection of DNA is lost, or deleted Frameshift Since protein-coding DNA is divided into codons three bases long, insertions and deletions can ‘shift’ the code
- 18. The Effects ofMutations All cells contain DNA = lots of places for a mutation to occur Somatic mutations occur in non-reproductive cells and won't be passed onto offspring
- 19. The Effects ofMutations Germ line mutations occur in reproductive cells like sperm and eggs and can be passed to offspring and has large scale effects on evolution The mutation could do nothing The mutation could do something small… The mutation could have large consequences… http://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_ 06