Chapters 8 & 9 DNA and Protein Synthesis The Central Dogma

1. Chapters 8 & 9DNA and Protein SynthesisThe Central Dogma

2. Experiments on DNA • We did this yesterday. (Or at least tried) • What to do with the post-it. • On the door place the post-it based on how well you understand the results of the experiments and the basics of how they worked. Top= I’m good: Bottom=What experiments? • If you have a specific question, Write it on the post-it.

10. Watson and Crick DNA Model • Double Helix • Twisted ladder formed of nucleotides. • Rungs of the ladder are nucleotide bases. • Base pairing rule: • Adenine -> Thymine : Cytosine -> Guanine

15. Watson and Crick continued… • Sides of the ladder are alternating deoxyribose sugars and phosphate groups • One page paper, the most important in biology since Darwin’s The Origin of Species.

17. DNA Replication: Semi-conservative replication (3 main steps) • DNA uncoils and unzips with help from Helicase (enz.) and exposes unpaired bases on 2 separate strands @ the replication fork. • New DNA nucleotides bond to the existing old strands with help from DNA Polymerase according to base pair rules. • Result: 2 New double helices formed. Each old strand paired up with a new strand.

19. Other DNA Replication Info • After step 2, DNA “proofreads” the strand to assure no mistakes are made. • DNA Rep. takes place during S-phase of Interphase, before cell division. • DNA Rep. can only extend existing DNA.

20. How DNA controls all • A trait (phenotype) is the physical expression of a gene. • Ex: visible characteristics, hair, height, etc. • A gene is a length of DNA which is the code to make a protein. • A chromosome is a whole series of genes (DNA segments) linked. • The nucleus contains all the chromosomes of the cell.

21. The nucleus controls the cell by containing DNA. How? • The DNA determines which proteins (enz.) will be made. • The enzymes determine which activities the cell will perform. • Analogy: Boss (DNA) tells (codes) the workers (Proteins) to do their job (Function)

23. Linkage Group • Genes on the same chromosome inherited together. • Ex: Everywhere A goes B goes too.

24. Crossing Over • An exchange of genes between homologous chromosomes during meiosis when two adjacent chromosomes have parts break free and reattach themselves to the other chromosome. • Results in new genetic combinations and adds to diversity of life.

25. A= Short B= Blonde Hair C= Blue Eyes a= Tall b= Brown Hair c= Brown Eyes 1 2 1=Short, Blonde Hair, Brown Eyes 2= Tall, Brown Hair, Blue Eyes

26. Multiple Gene • More than two genes are responsible for a trait. • AKA: Polygenic • Ex: Human skin color or eye color • 8 Genes are involved

28. 3 Forms of RNA • rRNA- makes up part of the ribosome. • tRNA- picks up specific aa in the cytoplasm and transfers them to the working ribosome to become part of a growing protein. • mRNA- brings the DNA message into the cytoplasm where a ribosome binds to it to begin the process of translation.

30. DNA vs. RNA • Deoxyribose Sugar • Thymine nucleotide base • Double Stranded • Ribose Sugar • Uracil nucleotide base • Single Stranded DNA RNA

33. Transcription • DNA uncoils and one side of the two strands is read by RNA Polymerase, which has helicase powers, to form a strand of mRNA. • The mRNA travels into the cytoplasm where ribosomes attach to it to start translation.

35. RNA Processing • Cap- Protective cap added to one end. • Poly A tail- add about 200-300 Adenines to the opposite end of the cap. • Splicing- cuts introns, leave exons (choose which exons to determine protein)

37. Translation • mRNA is read chemically by the ribosome. • In the process, tRNA is used to bring the correct aa from the cytoplasm to attach to the ribosome-mRNA complex and begin forming the protein. • The protein grows as aa brought in by the tRNA are added together in a long strand.

39. The tRNA bonds to a specific aa at one end and to a specific 3 base sequence on the mRNA called the codon on the other end. • This is the codon - anticodon pairing that ensures a maintenance of message from DNA to protein. • Codon- 3 consecutive mRNA bases that encode a specific aa. • Cannot be 1-1 because we have 20 aa.

40. Understanding how DNA makes RNA • Start with a strand of DNA segment and turn it into an mRNA segment. ATCGATGAGTGCGTAGCT = DNA Strand UAGCUACUCACGCAUCGA =RNA Strand created from the DNA Strand Instead of bringing in a T to pair with the A, a U would be brought in instead. All the other base pairing combinations stay the same.

41. How RNA makes Protein • We need to start by knowing the different parts. • UAGCUACUCACGCAUCGA = mRNA • This needs to be broken down into 3 consecutive bases that we call a codon. • UAG-CUA-CUC-ACG-CAU-CGA • This are the codon we would look up on the mRNA chart.

42. How the tRNA works • The tRNA contains an anti-codon stretch at one end of it’s structure. This binds to the codon on the mRNA. The tRNA anti-codon is the compliment of the mRNA. • You never look up the anti-codons on a chart. • UAG-CUA-CUC-ACG-CAU-CGA = mRNA • AUC-GAU-GAG-UGC-GUA-GCU= tRNA

46. Gene Expression • Prokaryotes- operon system • Its only on when its needed. • Read 190-191. • Eukaryotes • The same general principle as Prokaryotes. • Read 192-193

47. Lac Operon • The operon makes the enz. Lactase • Lactase digests the sugar lactose • When lactose is present the operon turns on. When not, it is turned off.

49. Homeotic and Oncogenes • Homeotic- master genes that control embryonic development. • Which parts of body from what parts • Oncogenes- genes that cause cancer • We may all have some we inherited.