1. DNA Structure and Protein Synthesis Topic 2.4

2. Introduction  Cause of CF?  faulty CFTR protein  What causes faulty protein?  DNA Mutation  What is a mutation?  Change in the DNA sequence.  What does DNA code for?  Proteins  What is the primary structure of a protein?  The sequence of amino acids

3. Introduction: Protein structure review  Primary Structure  Bonds formed between amino acids?  What type of reaction occurs when 2 amino acids join together?  What is the significance of the primary structure?  The sequence of amino acids in the chain determines the tertiary structure and therefore its shape and its function.

4. Secondary structure  What are the two forms of secondary structure?  Alpha helix: H bonds form between every 4th amino acid  Beta pleated sheets can also form: parallel chains joined by H bonds.

5. Tertiary structure  Proteins have precise 3D shapes.  Types of bonds/interactions?  interactions between R groups.  Covalent bonds (disulphide bridges)  Ionic bonds  Hydrogen bonds  Also hydrophilic and hydrophobic interactions

6. Quaternary structure  Proteins composed of more than 1 polypeptide chain also have quaternary structure

7. Introduction continued...  Define-  Gene:  a sequence of bases on a DNA molecule coding for 1 polypeptide  Genome:  all the genes of an organism  DNA:  deoxyribonucleic acid is a polymer.  Where is the DNA found?  nucleus

8. Nucleic acids: DNA & RNA PolymerMonomer Proteins Carbohydrates Lipids Nucleic Acids (DNA and RNA) Amino acid Monosaccharide Fatty acids and gylcerol Mononucleotides

9. Nucleotides  Nitrogenous base, pentose sugar (ribose or deoxyribose) and phosphate group Nucleotide

11.  Nucleotides join together and form a polynucleotide.  What type of reaction occurs?

12. DNA DNA = double strand Two sugar-phosphate backbones Held together by hydrogen bonds between the bases C only bonds with G A only bonds with T

13. DNA  What are the bases?  thymine, guanine, adenine and cytosine  Double stranded:  H bonds  Complementary bases ? A=T, C=G

14. Nitrogenous bases  Why is the DNA molecule the same width all the way along?  A and G are purines and larger  T and C are pyrimidines and smaller

15. Calculating the number of each base  If 20% of the nucleotides in a section of DNA containing 2000 base pairs are adenine, how many are cytosine?  4000 bases total  40% A and T so 60% are C and G  30% are C  30% of 4000= 1200  https://www.dnalc.org/resources/3d/21-chargaff-ratios.html

16. Why is DNA a double helix?  Helix: stable due to H bonds and helical structure  2 strands of DNA reduces chance of mutations Purpose of DNA  Order of the bases stores genetic information  Complementary base pairing enables replication and protein synthesis

17. The Central Dogma DNA can make identical copies of itself = replication RNA copies have to be made of active genes = transcription The base sequence gives the instructions to make proteins = translation

18. DNA cannot pass out of the nucleus

19. RNA: Ribonucleic acid  Ribose  Bases: U (uracil), A, G and C  Single stranded  3 types:  Messenger RNA,  Transfer RNA  ribosomal RNA

20. Genetic code  Define a gene:  What are proteins made of?  How do we get such vastly different protein from the same molecule – DNA?

21. Genetic Code  So what is the role of a gene?  The order of the bases in the DNA strand of a gene acts as a code that determines the order of amino acids in a protein.  Is the primary structure important?  The order of amino acids is the primary structure. This determines the tertiary structure, which determines the structure and function of a protein

22. Genetic code  Our genetic code is:  TUND  Triplet code - 3 bases on the DNA code for 1 amino acid  https://www.dnalc.org/resources /3d/10-triplet-code.html  Universal code: the same triplet codes for the same amino acid in ALL organisms  Non-overlapping : each base only belongs to one triplet: there is no overlap  Degenerative : there is more than 1 code for each amino acid

23. Protein Synthesis  DNA in nucleus.  Proteins made in cytoplasm:  How is this possible?  2 steps:  Transcription: production of mRNA- DNA → mRNA  Translation: using mRNA to produce protein- mRNA → primary structure of protein

24. Base triplets, Codons, Anticodons Base Triplet 3 bases in the DNA coding for one amino acid Codon 3 bases in the mRNA- complementary to a base triplet. Start codon triggers the start of translation, stop codon triggers the end. tRNA Transfer RNA: single stranded RNA folded into a clover leaf shape. Anticodon on one end and attachment site for specific amino acid at the opposite end- fig 2.38 Anticodon 3 bases in the t RNA- complementary to a codon

25. Protein synthesis

26. Transcription  http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302– first 4 slides http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302  https://www.dnalc.org/resources/3d/12-transcription-basic.html  Where does it take place?  What is produced?  How is it produced?  Anti-sense strand  Template strand  sense strand  Coding strand  Uracil.

27. Translation  mRNA  Ribosome subunits  Start codon  Two tRNA molecules  Complementary base pairing  Q 2.21-2.25  Specific amino acid  Peptide bond  Condensation  Ribosome moves along the mRNA one codon at a time  Stop codon  http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302 – complete filling in blanks http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302  Where does it take place?  What is produced?  How is it produced?

29. Translation

30. What is analogous to the following in protein synthesis? o master copy of a chocolate cake recipe? o DNA o photocopy of the recipe used in the kitchen/factory that day when the cake is made? o mRNA o ingredients? o Amino acids o person who buys the ingredients and brings to kitchen/factory? o tRNA o apparatus/equipment used to make the cake? o ribosomes