DNA & Protein Synthesis

1. DNA & Protein Synthesis

2. The student will investigate and understand common mechanisms of inheritance and protein synthesis. • Key concepts include: • f) the structure, function, and replication of nucleic acids (DNA and RNA); and • g) events involved in the construction of proteins.

3. The student will investigate and understand common mechanisms of inheritance and protein synthesis. • Key concepts include: • h) use, limitations, and misuse of genetic information; and • i) exploration of the impact of DNA technologies.

4. History • Before the 1940’s scientists didn’t know what material caused inheritance. • They suspected it was either DNA or proteins.

5. History • A series of experiments proved that DNA was the genetic material responsible for inheritance.

6. History • In 1952, Alfred Hershey and Martha Chase did an experiment using a virus that infects E. coli bacteria. • The experiment proved that DNA and not protein is the factor that influences inheritance.

8. History • Erwin Chargaff discovered the base pairing rules and ratios for different species. • Adenine pairs with Thymine • Cytosine pairs with Guanine.

9. History • Rosalind Franklin & Maurice Wilkins had taken the 1st pictures of DNA using X-ray crystallization

10. This proved that DNA had a helical shape.

11. History • The Nobel Prize in Medicine 1962 Francis Harry Compton Crick James Dewey Watson Rosalind Franklin (Died of cancer 1958) Maurice Hugh Frederick Wilkins

12. Wilkins has become a historical footnote and Watson & Crick are remembered as the Fathers of DNA Double Helix Watson Crick

15. Phosphate Group O O=P-O O Nitrogenous base (A, T,G, C) 5 CH2 O N Sugar (deoxyribose) C1 C4 C3 C2 DNA

16. Nitrogen Bases • 2 types of Nitrogen Bases • Purines • Double ring • G & A • Pyrimidines • Single ring • C & U & T PGA CUT PY

17. 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 1 2 3 5 O P P T T A A 3 5 O O 5 P P 3 DNA - double helix

18. DNA • The genetic code is a sequence of DNA nucleotides in the nucleus of cells.

19. DNA • DNA is a double-stranded molecule. • The strands are connected by complementary nucleotide pairs (A-T & C-G) like rungs on a ladder. • The ladder twists to form a double helix.

20. DNA • During S stage in interphase, DNA replicates itself. • DNA replication is a semi-conservative process.

21. DNA • Semi-conservative means that you conserve part of the original structure in the new one. • You end up with 2 identical strands of DNA.

22. DNA • Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc.) • A gene is a stretch of DNA.

23. DNA • A mistake in DNA replication is called a mutation. • Many enzymes are involved in finding and repairing mistakes.

24. Mutations • What causes mutations? • Can occur spontaneously • Can be caused by a mutagen • Mutagen: An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism.

25. Mutations • Some mutations can: • Have little to no effect • Be beneficial (produce organisms that are better suited to their environments) • Be deleterious (harmful)

26. Mutations • Types of mutations • Point Mutations or Substitutions: causes the replacement of a single base nucleotide with another nucleotide • Missense- code for a different amino acid • Nonsense- code for a stop, which can shorten the protein • Silent- code for the same amino acid (AA)

29. Mutations • Example: Sickle Cell Anemia

30. Mutations • Types of mutations • Frame Shift Mutations: the number of nucleotides inserted or deleted is not a multiple of three, so that every codon beyond the point of insertion or deletion is read incorrectly during translation. • Ex.: Crohn’s disease

31. Insertion Deletion

32. Mutations • Types of mutations • Chromosomal Inversions: an entire section of DNA is reversed. • Ex.: hemophilia, a bleeding disorder

34. DNA Repair • A complex system of enzymes, active in the G2 stage of interphase, serves as a back up to repair damaged DNA before it is dispersed into new cells during mitosis.

36. Phosphate Group O O=P-O O Nitrogenous base (A, U,G, C ) 5 CH2 O N Sugar (ribose) C1 C4 C3 C2 RNA

37. RNA • Function: obtain information from DNA & synthesizes proteins

38. 3 differences from DNA • Single strand instead of double strand • Ribose instead of deoxyribose • Uracil instead of thymine

39. 3 types of RNA • Messenger RNA (mRNA)- copies information from DNA for protein synthesis Codon- 3 base pairs that code for a single amino acid. codon

40. 3 types of RNA 2. Transfer RNA (tRNA)- collects amino acids for protein synthesis Anticodon-a sequence of 3 bases that are complementary base pairs to a codon in the mRNA

41. 3 types of RNA 3. Ribosomal RNA (rRNA)- combines with proteins to form ribosomes

42. Amino Acids • Amino acids- the building blocks of protein • At least one kind of tRNA is present for each of the 20 amino acids used in protein synthesis.

43. Transcription - mRNA is made from DNA & goes to the ribosome Translation - Proteins are made from the message on the mRNA

44. Transcription • In order for cells to make proteins, the DNA code must be transcribed (copied) to mRNA. • The mRNA carries the code from the nucleus to the ribosomes.

46. Translation • At the ribosome, amino acids (AA) are linked together to form specific proteins. • The amino acid sequence is directed by the mRNA molecule. Amino acids ribosome

48. Make A Protein • DNA sequence ATG AAA AAC AAG GTA TAG • mRNA sequence UAC UUU UUG UUC CAU AUC

49. Make mRNA • mRNA sequence UAC UUU UUG UUC CAU AUC • tRNA sequence AUG AAA AAC AAG GUA UAG