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Chapter 8

Chapter 8 . From DNA to Proteins 2 Types of nucleic acid. DNA- Life’s Code. DNA -> RNA -> Protein. Influential Scientists. Frederick Griffith – Experimented with two forms of bacteria that cause pneumonia on mice Smooth (S) and Rough (R) Demonstrated Transformation

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Chapter 8

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  1. Chapter 8 From DNA to Proteins 2 Types of nucleic acid

  2. DNA- Life’s Code DNA -> RNA -> Protein

  3. Influential Scientists • Frederick Griffith – Experimented with two forms of bacteria that cause pneumonia on mice • Smooth (S) and Rough (R) • Demonstrated Transformation • His conclusion: some factor changed the bacteria • “Transforming Principal”

  4. Influential Scientists • Oswald Avery – Was puzzled by Griffith’s discovery and worked for 10 years to find the answer. • Directly observed transformation of R bacteria into S bacteria • Concluded that DNA is the transforming principal • DNA = Genetic material

  5. Influential Scientists • HersheyandChase- supported the conclusion - DNA is the source of genetic information • Used bacteriophage infected with radioactive sulfur atoms on protein. • Bacteriophage – a virus that infects and replicates within bacteria. • Minimal radioactivity found in bacteria • Used bacteriophage infected with radioactive phosphorus atoms on DNA. • Radioactivity found in bacteria

  6. 2 Types of Nucleic AcidsDNA and RNA • DNA • DNA stands for Deoxyribo Nucleic Acid • DNA is genetic material that determines inherited characteristics/traits • The job of DNA is to code for proteins in the body.

  7. DNA Structure • What is the monomer that makes up DNA? • DNA is made up of long chains of Nucleotides. • Nucleotides- make up genes that code for a specific trait. • What makes up a Nucleotide? • 1. Deoxyribose sugar ( ) • 2. Phosphate ( ) • 3. Nitrogen Base • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T)

  8. Structure of DNA • Double Helix – Spiral ladder • Discovered by Watson and Crick in the 1950’s with the help of Franklin’s x-ray pictures • Double stranded • Complementary base paring – the nitrogen bases on one side of the ladder ALWAYS pair up with the same nitrogen base on the other side of the ladder. • Discovered by Chargaff • The pairs are held together with hydrogen bonds A  T G  C

  9. Review • How many different types of nucleotides are there? How do they differ? • What is the monomer of DNA? • What does DNA stand for? • DNA’s shape can be described as a ______________? • What makes up the sides of DNA? • What makes up the rungs?

  10. DNA Replication • Remember: DNA is always copied during cell reproduction • Mitosis • This takes place during the S phase of Interphase

  11. Steps to DNA Replication • 1. The DNA molecule is split down the middle (at the nitrogen bases) by helicase, breaking the hydrogen bonds. • Similar to a zipper • 2. The nitrogen bases on each side of the molecule are used as a pattern for a new strand. • 3. Complementary bases are added to each individual strand by DNA polymerase (enzyme). • Each new cell can now get a complete copy of all the DNA. • One of the original strand, one new

  12. Figure 8.8

  13. Practice Base-Paring • Original strand: ATTCCG • Complement: • Original strand: GCTAAG • Complementary strand: • Original strand: CTACCA • Complement: • Original: • Strand A: GACCTA • Strand B:

  14. nucleotide new strand DNA polymerase Review • What is the purpose of replication? • How does DNA serve as its own template?

  15. Central Dogma • DNA RNA  Protein Transcription DNA  RNA Translation RNA  Protein

  16. DNA makes RNA • RNA is the 2nd type of Nucleic Acid • RNA is made of nucleotides, just like DNA • 1. Ribose is the sugar • 2. Phosphate • 3. Nitrogen Bases • Adenine (A) • Guanine (G) • Cytosine (C) • Uracil (U): NOT Thymine (T) • Single Stranded • When RNA is assembled based off of DNA’s pattern, this is called Transcription

  17. DNA Transcription DNA is too large to get out of the nucleus, RNA carries DNA’s message out of the nucleus to a ribosome. Ribosome – where the protein will be made. • Occurs in the nucleus • DNA is again unzipped by helicase. • RNA Polymerase adds complementary RNA nucleotides • This makes mRNA • mRNA = messenger = carries the message • mRNA leaves the nucleus

  18. RNA complimentary base pairingduring Transcription • DNA strand = AATTTGCGCGGCT • mRNA strand = • DNA strand = TATGCGCACTG • mRNA strand = • DNA strand = CGATCAGCCTAT • mRNA strand =

  19. Transcription

  20. 3 Types of RNA

  21. Translation • RNA to Protein • Translation converts mRNA messages into Polypeptides • String of amino acids held together by a peptide bond • A codon is a sequence of three nucleotides that codes for an amino acid. • Examples: • AUG= Methionine • CUU= Leucine

  22. The Genetic Code • The genetic code matches the mRNA codon with the amino acid or action • AUG= Start/ Methionine • UAA, UGA or UAG= Stop • Codon GCA = • Codon AAG = • Codon CUG = • Codon CGA =

  23. Translation • mRNA carries the DNA instructions for making protein • mRNA goes into the cytoplasm • mRNA attaches to a ribosome to be “read” • Ribosomal RNA (rRNA) • Appropriate amino acids are strung together to build a polypeptide chain by reading codons. • Amino acids are attached to Transfer RNA (tRNA) • tRNA is complementary to mRNA • mRNA strand - ACC • tRNA strand = • mRNA strand - GUC • tRNA strand = • Polypeptide chain = protein

  24. Translation

  25. Translation

  26. Translation

  27. Review • What are the three parts to the Central Dogma? • How is RNA similar to DNA? • How is RNA different from DNA? • What are the 3 types of RNA?

  28. Mutations • There are two types of mutations • Sex cell mutations: affect the offspring • Body cell mutations: affect the individual only • Lethal mutations vs. beneficial mutations • Most mutations are good • DNA Polymerase can usually detect errors

  29. Causes of Mutations • Mistakes in base paring during DNA Replication • Cause of many genetic disorders • Insertions and deletions • Chemicals: like tobacco • Can lead to cancer because it changes the genes that regulate mitosis • Radiation: including UV (sun) and X-ray • Can lead to cancer because it changes the genes that regulate mitosis

  30. Point Mutations • 1. Substitution • Point where one nitrogen base is substituted for another • Sickle Cell Anemia: substitute A for T

  31. Frame Shift Mutations • 2. Deletions and insertions • When a nitrogen base is deleted or added • Frame shift mutations- because it moves the codon up or down • Changes the sequence of amino acids

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