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Unit 6

Unit 6. DNA. Griffith Experiment. DNA Structure. DNA is a polymer made of monomers called nucleotides Each nucleotide is made of: A phosphate group Deoxyribose (sugar) Nitrogen containing base. DNA Structure. DNA is in the shape of a double helix Each nucleotide is paired.

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Unit 6

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  1. Unit 6 DNA

  2. Griffith Experiment

  3. DNA Structure • DNA is a polymer made of monomers called nucleotides • Each nucleotide is made of: • A phosphate group • Deoxyribose (sugar) • Nitrogen containing base

  4. DNA Structure • DNA is in the shape of a double helix • Each nucleotide is paired

  5. Types of Nucleotides • C – Cytosine Pyrimidines • T – Thymine • A – Adenine Purines • G – Guanine

  6. Base-Pairing Rules • Nucleotides always pair in the same way • Thymine (T) always pairs with Adenine (A) • Cytosine (C) always pairs with Guanine (G) • Ex. TTACGTAG AATGCATC

  7. DNA Replication • Replication is a process by which DNA is copied • Occurs during the S stage of the cell cycle

  8. DNA Replication • Enzymes are responsible for splitting and copying DNA • DNA polymerase- enzyme that binds DNA strands together

  9. DNA _________ Replication • Steps of Replication: • DNA strand is unzipped • Free nucleotides bind to each template strand • Two identical DNA strands are formed

  10. DNA Transcription • Transcription is the process of copying a sequence of DNA into a message called RNA • RNA is a temporary copy of DNA • Three types of RNA: • mRNA- message • rRNA- forms part of ribosomes • tRNA- transfers amino acids to help make proteins

  11. DNA Transcription Transcription Animation • Steps of transcription: • Gene is recognized, DNA unwinds • RNA strand binds to template strand - GC, TA, AU (not T) • Completed RNA strand separates

  12. DNA Translation • Translation- process converts, mRNA message into a polypeptide • Polypeptides make up proteins • Codon- 3 nucleotide sequence that codes for an amino acid

  13. DNA Translation

  14. Steps of Translation The start mRNA codon attracts a complimentary tRNAanticodon Each amino acid is added to the next tRNA Process continues until a stop codon is reached. Protein is then released

  15. Gene Expression • Genes can make a lot of protein, little, or none • Transcription is controlled by promoters and operators • Promoter- DNA segment that allows a gene to be transcribed • Operator- DNA segment turns a gene “on” or “off”

  16. Gene Expression • Operon- • region of DNA that includes a promoter, operator and genes that code for certain proteins

  17. mRNA Processing • Sometimes pieces of mRNA are not needed • Introns are removed • A cap and tail are added • Molecule joins together

  18. Mutations • mutation- change in an organism’s DNA • Single gene mutations usually occur in replication • Mutations affecting a group of genes happen in meiosis

  19. Mutations • Types of mutations: • Point mutation- one nucleotide is substituted for another • Frameshift mutation • Insertion- addition of a nucleotide • Deletion- removal of a nucleotide • Gene duplication • Gene translocation

  20. Point mutation Gene duplication Frameshift Translocation

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