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DNA, RNA, & Protein Synthesis

DNA, RNA, & Protein Synthesis. Unit4 – Lecture3. DNA . DNA = De-oxy-ribo-nucleic Acid “blueprint” for traits double helix shape composition: polymer of nucleotide monomers nucleotide [3 parts]: sugar [deoxyribose] phosphate nitrogen base. Nitrogen Bases. Nitrogen Bases:

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DNA, RNA, & Protein Synthesis

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  1. DNA, RNA, & Protein Synthesis Unit4 – Lecture3

  2. DNA • DNA = De-oxy-ribo-nucleic Acid • “blueprint” for traits • double helix shape • composition: • polymer of nucleotide monomers • nucleotide [3 parts]: • sugar [deoxyribose] • phosphate • nitrogen base

  3. Nitrogen Bases • Nitrogen Bases: • are complementary: • adenine [A] bonds with • thymine [T] • cytosine [C] bonds with • guanine [G]

  4. Nitrogen Bases – cont’d • Nitrogen Bases: • amount of A = amount of T • amount of C = amount of G • purines: A & G • pyrimidines: C & T

  5. Discuss • With what you just learned, find the answer to the following math problem: If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain?

  6. Discuss If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain? if A = 12% then T = 12% total = 24% A&T 100% - 24% = amount of C&G 76% = amount of C&G 76 / 2 = amount of C or amount of G C = 38%, G = 38%

  7. DNA – cont’d • Watson & Crick [1953] • proposed the structure of DNA • stole the work of Rosalind Franklin • X-Ray Crystallography

  8. DNA Replication • happens in the cell nucleus • occurs during interphase

  9. DNA Replication – cont’d • enzyme unzips DNA double strand by breaking the hydrogen bonds between bases • free-floating bases bond to open DNA

  10. DNA Replication – cont’d • continues… • end result = 2 strands, ½ new & ½ old DNA • repeat.

  11. RNA • RNA – Ribo-nucleic Acid • sugar = ribose [instead of deoxyribose] • single stranded • has nitrogen base Uracil instead of Thymine • A bonds with U • C bonds with G

  12. Discuss • Restate to your partner what the three differences are between RNA and DNA.

  13. RNA – cont’d • [RNA] • three types: • mRNA – messenger • complementary to DNA • ferries DNA’s message out of the nucleus • contains codons • codon – segment of three bases in mRNA • 1 codon = 1 amino acid or “start” or “stop” • 20-some of them exist

  14. Codon Chart

  15. RNA – cont’d • [RNA] • [three types:] • tRNA – transfer • ferries amino acids to ribosome • contains “anticodons” • complementary to mRNA • rRNA – ribosomal • makes up the ribosomes

  16. RNA – cont’d • [RNA] • [three types:] • rRNA – ribosomal • makes up the ribosomes

  17. Discuss • Name and explain the three types of rna to your partner.

  18. Protein Synthesis • transCription • DNA  mRNA • occurs in the nucleus • process begins at “promoter” • promoter tells where to start copying DNA sequence

  19. Protein Synthesis • transCription • enzyme unzips DNA but RNA bases pair instead of DNA bases • complementary bases are added

  20. Protein Synthesis • transCription • continue adding bases until a “termination sequence” is located. • mRNA carries message outside of the nucleus through nuclear pores into the cytoplasm

  21. Protein Synthesis • transLation • mRNA  protein • ribosomes read mRNA and use tRNA to make proteins • steps:

  22. Protein Synthesis • transLation • ribosomes clamp onto mRNA strand • finds “start” codon [AUG] • tRNA molecule containing matching anti-codon moves to ribosome • tRNA enters ribosome; attaches to strand

  23. Protein Synthesis • transLation • another tRNA enters ribosome • ribosome bonds amino acids [peptide bond] • first tRNA leaves, another enters • repeat until “stop” codon is reached

  24. Write this down! Any nitrogen bases that are BEFORE the “start” or AFTER the “stop” are NOT translated into amino acids.

  25. Protein Synthesis • transLation • result – chain of amino acids linked by peptide bonds • = polypeptide • = protein • polypeptide processed and shipped using ER & Golgi.

  26. Let’s Try It • C C A T A C G G T G T C T C C G A T A T T T T A • is this DNA or RNA? how do you know? • transcribe the DNA into mRNA • C C A T A C G G T G T C T C C G A T A T T T T A • G G U A U G C C A C A G A G G C U A U A A A A U • find the start codon [AUG] • G G U A U G C C A C A G A G G C U A U A A A A U

  27. Let’s Try It • G G U A U G C C A C A G A G G C U A U A AAA U • beginning with AUG, separate your mRNA into codons. • A U G / C C A / C A G / A G G/ C U A / U A A / A A U • beginning with your AUG, translate your mRNA into amino acids • keep translating until “stop” codon is reached

  28. Codon Chart

  29. Let’s Try It • A U G / C C A / C A G / A G G/ C U A / U A A / A A U • MET / PRO / GLN / ARG / LEU / (stop) 

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