DNA Replication & Protein Synthesis

1. DNA Replication & Protein Synthesis

2. History • Before the 1940’s scientists didn’t know what material caused inheritance. • They suspected it was either DNA or proteins. • A series of experiments proved that DNA was the genetic material responsible for inheritance.

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

4. Nitrogen Bases • 2 types of Nitrogen Bases • Purines • Double ring • G & A • Pyrimidines • Single ring • C & U & T

5. 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

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

7. 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. • Held together by H-bonds

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

9. DNA • Semi-conservative means that you conserve part of the original structure in the new one. • Each is half new and half original • You end up with 2 identical strands of DNA that are identical to the original

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

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

12. 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.

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

14. 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)

17. Mutations • Example: Sickle Cell Anemia

18. 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

19. Insertion Deletion

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

22. 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.

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

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

25. 3 differences from DNA • Single strand instead of double strand • Ribose instead of deoxyribose • Uracil instead of thymine

26. 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

27. 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

28. 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.

29. 3 types of RNA 3. Ribosomal RNA (rRNA)- combines with proteins to form ribosomes

30. Transcription - mRNA is made from DNA in the nucleus Translation - Proteins are made from mRNA at the ribosome in the cytoplasm

31. 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.

33. 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

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

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

38. Make mRNA • tRNA sequence AUG AAA AAC AAG GUA UAG • Amino Acid sequence met lys asn lys val stop