Unraveling the Mystery of DNA: Structure, Replication, and Protein Synthesis

1. DNA and RNA Ch 11

2. DNA • To know how genes work • we must know what they are made of.

3. Who helped to discover DNA? • Griffin (1928) discovered Transformation (genetic information transferred) through mouse experiment • Avery (1944) discovered DNA stores & transmits genetic information from 1 generation to next

4. Who helped discover DNA? • Hershey-Chase Experiment (1952)- used bacteriophage (virus that eats bacteria) to discover that the genetic material in the virus was the DNA Now we know that genes are made of DNA- but how does DNA give us all that info???

5. Components & Structure of DNA • DNA made of units called Nucleotides

6. 4 types of different nitrogenous bases: that fall in 2 categories: • Purines: 1. Adenine 2. Guanine • Pyrimidines: 3. Thymine 4. Cytosine We still don’t know how DNA was arranged!!

7. Discovery of DNA structure • Rosalind Franklin (1950’s): studied DNA using a technique called x-ray diffraction. • Her work was key to Watson & Cricks work

8. Discovery of DNA structure • Watson & Crick (1953): developed the double helix model of the structure of DNA

9. Double-Helix Structure • Bases of nucleotides are paired together • Attached by sugar phosphate backbone

11. Chromosomes & DNA Replication • DNA very long! The total length of DNA present in one adult human  is the equivalent distance from the earth to the sun and back.

12. Chromosome Structure • Contain DNA & proteins (called histones) packed together called Chromatin

14. DNA Replication • DNA must then replicate (copy) itself for cell division. • The 2 strands of DNA are called complimentarybecause Adenine Thymine Guanine Cytosine.

15. Replication • Begins when an enzyme (DNA polymerase) breaks apart the hydrogen bonds that hold the bases together  two strands begin to come apart.

16. As the DNA “unzips”, nucleotides attach to the exposed bases on the original DNA strand. • This process continues until the whole molecule has been unzipped and then replicated or copied.

17. The result of replication is two new strands of DNA exactly like the original!

18. RNA & Protein Synthesis • DNA provides the information necessary to produce all of the proteins in our body.

19. These proteins are used for: • Muscle tissue • Walls of blood vessels • Enzymes • Hair and more! • In this way, DNA controls the cell

20. RNA • RNA is essential in the production of proteins • Similar to DNA: but has 3 main differences • Uracil instead of Thymine • Single strand, not double strand • Ribose instead of deoxyribose • Ribonucleic Acid

22. Types of RNA • Carries copies of info from nucleus to the site of protein synthesis in the cytoplasm. • Compared to workers on an assembly line • SINGLE STRANDED! ***The production of mRNA from DNA happens in a process called transcription. • Messenger RNA (mRNA):

24. Types of RNA 2. Ribosomal RNA (rRNA): makes up ribosome • Considered the tools or the builder that puts together the proteins • The ribosomes clamp onto the mRNA and become the site for protein synthesis. • Clumped, single stranded form of RNA

26. Types of RNA 3. Transfer RNA (tRNA): transfers each amino acid (a.a.) to the ribosome • found in cytoplasm. • Folded, single stranded form of RNA • Attaches to and then transports the amino acid. to the site of protein synthesis at the ribosome

27. Each piece of tRNA only attaches to one and only one specific amino acid attached to a 3 letter Anticodon.

29. Transcription • The process of making mRNA from strands of original DNA to transport genetic material into the cytoplasm for protein synthesis. Where? Prokaryotic cells: occurs in the cytoplasm Eukaryotic cells: occurs in the nucleus

30. Steps of Transcription • 1 ) RNA polymerase attaches to DNA chains at promoter locations (specific genes). * Start CODON ( AUG ) • 2 ) DNA chains continue to unwind and are transcripted until a termination signal is reached ( specific sequence of nucleotides ) • *Stop CODON ( UAA, UAG, UGA ) • 3) mRNA chains in eukaryotes pass through the nuclear pores to the cytosol

31. Promoters: regions in DNA that tell DNA polymerase when to start & stop Codon: 3 letter combination on the mRNA strand that codes for a specific amino acid.

32. RNA Editing • Introns: pieces of DNA that is NOT “read” to make proteins • Copied into mRNA, then taken out! • Exons: DNA that is coded (read) to make proteins

33. Protein Synthesis (Translation) Remember – proteins are one type of organic compound (made up of polypeptides of amino acids) • During protein synthesis mRNA transcript is translated into amino acid sequences = GENETIC CODE • 3 NUCLEOTIDE SEQUENCE AMINO ACID = CODON

34. The Steps of Protein Synthesis • mRNA codons attract specific tRNA anticodons to attach to the mRNA strand 2) Each tRNA molecule brings a specific amino acid which then connect together to form an amino acid chain.

35. Protein Synthesis A codon chart allows us to know what amino acid a tRNA molecule will bring according to the 3 nucleotide sequence on the mRNA strand.

36. The Genetic Code • Remember: amino acidsmake up proteins called polypeptides. • Language of mRNA is the genetic code • A, U , C, G • Codon: 3 nucleotides (in order) that codes for a certain amino acid • Ex. A-G-C or C-C-C

37. From DNA to Protein Prokaryotes DNA—mRNA—tRNA—PROTEIN ( Cytosol ) Eukaryotes DNA—mRNA—tRNA--PROTEIN ( ribosomes) - The same for slugs, bugs, potatoes, tomatoes and every other living thing!

38. Mutations • Changes in genetic material • Mutagen: Anything that causes a mutation in DNA. • Ex. X-Rays, UV Radiation, Nuclear Radiation, Cosmic Rays, Asbestos, Cyanide, Benzene

39. Kinds of Mutations Gene Mutations • Frameshift • GATTACAGC…  GTTACAGCA… • MY DOG SKIP  MD OGS KIP • Point • GCATTG  GCAATG • MY DOG SKIP  ME DOG SKIP