Protein Synthesis

1. Protein Synthesis DNA & RNA

2. DNA • Deoxyribonucleic Acid • Shape - double helix - twisted ladder

4. DNA cont. • Made up of three parts • A sugar molecule - deoxyribose • A phosphate group • A nitrogen base • Adenine • Guanine • Cytosine • Thymine

7. Bases • Purines - 2 rings of carbon and nitrogen atoms • Adenine • Guanine • Pyrimidines - 1 ring of carbon and nitrogen atoms • Thymine • Cytosine

8. Purines

10. Complementary Base Pairing • Nucleotides that normally pair together • 2 Base-pairing rules • Cytosine bonds with guanine • Adenine bonds with thymine • Base pairs connect by hydrogen bonds

12. The DNA Songto the tune of "Row, Row, Row your Boat We love DNA, made of nucleotides. Sugar, phosphate and a base bonded down one side. Adenine and thymine make a lovely pair, cytosine without guanine would feel very bare.

13. Replication of DNA • Replication= process of copying DNA in the cell. • 1. Two nucleotide chains are separated by helicase enzyme. (AKA replication fork) • 2. Hydrogen bonds within DNA are broken. • 3. DNA polymerases attached to strands. • 4. Complimentary DNA strands are formed. • 5. New strands bind with old strands resulting in two full strands of DNA.

15. RNA • Ribonucleic Acid • Shape - Single helix

16. RNA

17. Three Type of RNA • Messanger RNA (mRNA) • Carries genetic material from DNA in the nucleus to the cytosol. • Transfer RNA (tRNA) • Hairpin shaped. • Binds directly to amino acids. • Ribosomal RNA (rRNA) • Most abundant type of RNA • Assist in production of proteins

18. RNA cont. • Made up of three parts • A sugar molecule - ribose • A phosphate group • A nitrogen base • Adenine • Guanine • Cytosine • Uracil

21. Purine or Pyridimine?

22. Pyridimine

23. Complementary Base Pairing • 2 Base-pairing rules • Cytosine bonds with guanine • Adenine bonds with URACIL

24. Protein Synthesis

25. General Information • One strand of the DNA double helix is used as a template • DNA is only found in the nucleus • Protein synthesis takes place in ribosomes.

26. Transcription

27. Breaking the Bonds • RNA polymerase bumps into the promotor site of the DNA • Helicase is an enzyme used to unzip the DNA • Occurs inside the nucleus!

29. Breaking the Bonds cont. • Messenger RNA (mRNA) is synthesized by RNA polymerase until a stop signal is reached.

31. After mRNA is Made • Helix zips the DNA molecule as hydrogen bonds form • mRNA leaves the nucleus

32. mRNA • mRNA leaves the nucleus through pores in the nuclear membrane and travels to the cytoplasm • Every 3 bases make what is known as a codon • Look on page 195 of text

34. 2 n d 3rd 1st

35. Something to notice • There is only one start codon. • For translation to occur, mRNA must have AUG. • There are three stop codons. • Translation will stop if mRNA reaches UAA, UAG or UGA.

36. Translation

38. Translation • Ribosomes bind with the mRNA at the start codon (AUG) • tRNA (transfer RNA) has an anticodon (three nitrogenous bases that are complementary to the codon on mRNA) that codes for the same amino acid.

40. Translation cont. • tRNA finds the amino acid that the genetic code asks for and bring it to the ribosomes.

41. Translation • What would the tRNA sequence be?

42. Translation cont. • The ribosomes build peptide bonds connecting the amino acids to form a polypeptide.

43. Protein Elongation

44. Ending Translation • At the end, the stop codon terminates translation • The complete polypeptide is released from the ribosome.

45. Termination of Translation • What would the peptide sequence be?

46. How many stop codons are there?

48. Summary of Translation

49. Recap

50. Proteins Synthesis • DNA is “unzipped” • mRNA is made and leaves the nucleus • tRNA takes the amino acids to the ribosomes • Protein is made