1. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Genetic Code The genetic code is the set of rules relating nucleotide sequence to amino acid sequence. The genetic code is shared by all organisms.

2. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

3. DNA specifies the synthesis of proteins in two stages: –Transcription –Translation

4. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings From Nucleotides to Amino Acids: An Overview Genetic information in DNA is transcribed into RNA and then translated into polypeptides. What is the language of nucleic acids? –In DNA, it is the linear sequence of nucleotide bases.

5. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Transcription: From DNA to RNA In transcription, –Genetic information is transferred from DNA to mRNA. –An mRNA molecule is transcribed from a DNA template. http://www.stolaf.edu/people/giannini/flash animat/molgenetics/transcription.swf

6. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings When DNA is transcribed, the result is an mRNA molecule. RNA is then translated into a sequence of amino acids in a polypeptide.

7. Figure 10.13a

8. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Transcribe this DNA template into a strand of RNA: TAC AAC TAT TTT CGC CCG CGG ATT AUG UUG AUA AAA GCG GGC GCC UAA

9. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Answers to study guide page 59 I.Review the structure of DNA 1.DNA is a polymer called a nucleic acid. 2. The repeating units of DNA are called nucleotides. 3.Each DNA nucleotide is made of a phosphate, a deoxyribose, and a nitrogen base. 4.

10. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Answers to study guide page 45 (continued) 5. How many nitrogen bases are possible in DNA? 4 Name them. A, T, G, C How do the bases pair? A-T, G-C What kind of bonds hold the bases together? Hydrogen 6.What is the shape of the molecule? Double helix 7. Where in the cell would you find DNA? nucleus

11. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Answers to study guide page 45 (continued) II. Describe the structure of RNA 1.RNA is a polymer called a nucleic acid. 2. The repeating units of RNA are called nucleotides. 3.Each RNA nucleotide is made of a phosphate, a ribose, and a nitrogen base. 4.

12. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Answers to study guide page 45 (continued) 5. How many nitrogen bases are possible in RNA? 4 Name them. A, U, G, C How do the bases pair? A-U, G-C What kind of bonds hold the bases together? Hydrogen 6.What is the shape of the molecule? Single stranded, can form a ribosome or transfer RNA 7. Where in the cell would you find DNA? Nucleus and Cytoplasm

13. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings III. Compare and Contrast DNA & RNA Nucleic Acid Type of Sugar Bases Possible ShapeLocation in Cell DNAdeoxyriboseA, T, G, CDouble helixnucleus RNAriboseA, U, G, CSingle stranded Nucleus & cytoplasm

14. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings IV. Three types of RNA Type of RNALocation in CellFunction Messenger RNANucleus & CytoplasmCarry “message” from DNA in the nucleus Transfer RNACytoplasmDeliver amino acids to the mRNA Ribosomal RNACytoplasm (originally made in nucleolus) Site of translation (pairs tRNA with mRNA)

15. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Protein Synthesis The two steps in protein synthesis are: -transcription- RNA polymerase transcribes a gene (section of DNA) into a single strand of messenger RNA - translation- messenger RNA codes for a sequence of amino acids which make up a protein

16. Figure 10.10

17. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Messenger RNA (mRNA) mRNA carries the code in triplets of bases –Specify all the amino acids. –Are called codons.

18. Figure 10.11

19. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Transfer RNA (tRNA) tRNA –delivers amino acids. –Matches amino acids with codons in mRNA using anticodons.

20. Figure 10.15

21. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Ribosomes –Are structures that actually make proteins. –Contain ribosomal RNA (rRNA). –May be free floating or attached to the endoplasmic reticulum.

22. Figure 10.16a

23. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings A fully assembled ribosome holds tRNA and mRNA for use in translation.

24. Figure 10.16b

25. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Translation: The Process Translation is divided into three phases: –Initiation -first amino acid attaches at start codon –Elongation- additional amino acids added –Termination- ribosome reaches stop codon –Chain of amino acids complete http://www.stolaf.edu/people/giannini/flashanimat/ molgenetics/translation.swf

26. Figure 10.20

27. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations A mutation –Is any change in the nucleotide sequence of DNA. –Point mutations- one nitrogen base is substituted for another (also called a base substitution)

28. Figure 10.21

29. Figure 10.22a

30. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Base deletions- a nucleotide is deleted (removed) from the sequence Base insertions- a nucleotide is added to the sequence Insertions and deletions –Can have disastrous effects. –Change the reading frame of the genetic message.

31. Figure 10.22b

32. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutagens Mutations may result from –Errors in DNA replication. –Physical or chemical agents called mutagens. Radiation High Temperatures A variety of chemicals –These external agents that cause mutations are called mutagens.

33. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings More Important Facts Mutagens break the chemical bonds of DNA or cause unusual bonds to form. A mutated gene will copy itself. AND, if this mistake is copied into a sex cell (gamete), then the mistake will affect the next generation. Mutated body cells CANNOT pass on mutations to next generation.

34. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Although mutations are often harmful, –They are the source of the rich diversity of genes in the living world. –They contribute to the process of evolution by natural selection.