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 _________ Steps of Replication: 1.DNA strand is unzipped 2.Free nucleotides bind to each template strand 3.Two identical DNA strands are formed Replication

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: 1.mRNA- message 2.rRNA- forms part of ribosomes 3.tRNA- transfers amino acids to help make proteins

11. DNA Transcription Steps of transcription: 1.Gene is recognized, DNA unwinds 2.RNA strand binds to template strand - G  C, T  A, A  U (not T) 3.Completed RNA strand separates Transcription Animation

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 1.The start mRNA codon attracts a complimentary tRNA anticodon 2.Each amino acid is added to the next tRNA 3.Process continues until a stop codon is reached. 4.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 1.Introns are removed 2.A cap and tail are added 3.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: 1.Point mutation- one nucleotide is substituted for another 2.Frameshift mutation 1.Insertion- addition of a nucleotide 2.Deletion- removal of a nucleotide 3.Gene duplication 4.Gene translocation

20. Point mutation Gene duplication Frameshift Translocation