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DNA

DNA. "The Blueprint of Life". DNA stands for... D eoxyribo N ucleic A cid. DNA FACTS. established by James Watso n and Francis Crick  Shape of a double helix. codes for your genes   (traits) made of repeating subunits called nucleotides. What is a nucleotide?. Has three parts:   

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DNA

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  1. DNA "The Blueprint of Life"

  2. DNA stands for...DeoxyriboNucleic Acid

  3. DNA FACTS • established by James Watson and Francis Crick  • Shape of a double helix

  4. codes for your genes  (traits) • made of repeating subunits called nucleotides

  5. What is a nucleotide? Has three parts:    PHOSPHATE DEOXYRIBOSE (sugar) BASE  (A,T,G,C)

  6. Base-Pair Rule Adenine <==> Thymine Guanine <==> Cytosine The sides of the DNA ladder are phosphate & sugar held together by  hydrogen bonds

  7. Base Pair Rule One side:     A   T   A      T   C   A      T   G   C      G   G   G Other side:

  8. How the Code Works The combination of A,T,G,C determines what traits you might have, for example: C A T C A T   =  purple hair T A C T A C  =  yellow hair

  9. Think of the bases of DNA like letters.Letters form words....Words form sentences....              *endless               combinations

  10. DNA REPLICATION the process by which DNA makes a copy of itself (cell division) SEMI-CONSERVATIVE - half of the old strand is saved

  11. http://207.207.4.198/pub/flash/24/menu.swf DNA Replication • Step 1: An enzyme (helicase) breaks the hydrogen bonds between nitrogen bases and the double helix “unzips” • Step 2: Another enzyme (DNApolymerase) moves along each strand and attaches new bases. This enzyme also proofreads the DNA for errors and may be able to correct simple errors. How Nucleotides are Added in DNA Replication DNA Replication Fork

  12. DNA Double stranded Deoxyribose sugar Bases: C,G A,T RNA Single stranded Ribose sugar Bases: C,G,A,U DNA vs. RNA Both contain a sugar, phosphate, and base.

  13. RNA Function • Three forms of RNA involved in protein synthesis: • mRNA (messenger) – copies instructions in DNA and carries these to the ribosome • tRNA (transfer) – carries amino acids to the ribosome • rRNA (ribosomal) composes the ribosome

  14. Protein Synthesis Transcription (DNA  RNA) & Translation (RNA  protein)

  15. Protein structure: • A string of amino acids linked by peptide bonds • 20 amino acids are arranged in different orders to make a variety of proteins

  16. Process of Transcription (1 of 2) • RNA polymerase unzips a section of DNA (usually a single gene) from a chromosome. • RNA polymerase pairs free RNA nucleotides to the exposed bases of one of the DNA strands following base pair rules. • Uracil replaces Thymine • Only 1 strand of DNA serves as a template; the other “hangs out”

  17. Process of Transcription (2 of 2) 3. Newly synthesized mRNA separates from template DNA and DNA zips back up. 4. mRNA strand with instructions for building a protein leaves the nucleus and goes to the cytoplasm.

  18. Transcription Practice • Transcribe the following DNA sequences into its mRNA DNA: TAC CGG ATC CTA GGA TCA mRNA: AUG GCC UAG GAU CCU AGU DNA: TAC CTT GTG CAT GGG ATC mRNA: AUG GAA CAC GUA CCC UAG

  19. Process of Translation (1 of 2) 1. mRNA binds to the ribosome. 2. Ribosome searches for start codon (AUG) 3. tRNA brings correct amino acid (methionine) to the ribosome. • Each tRNA carries one type of amino acid. • The anticodon (3 nitrogen bases on tRNA) must complement codon for amino acid to be added to protein chain.

  20. Process of Translation (2 of 2) 4. Ribosome reads the next codon 5. tRNA’s continue lining up amino acids according to codons 6. Peptide bondslink amino acids together 7. Ribosome reaches STOP codon (UAA, UAG, UGA) • Amino acid chain (protein) is released

  21. Reading the DNA code • Every 3 DNA bases pairs with 3 mRNA bases • Every group of 3 mRNA bases encodes a single amino acid • Codon - coding triplet of mRNA bases

  22. Which codons code for which amino acids? is an inventory of linkages between mRNA codons (nucleotide triplets) and the amino acids they code for

  23. Translation Practice • Read the mRNA codon • Find the • “1st base in the codon” on the left • “2nd base in the codon” on the top • “3rd base in the codon” on the right • Read the amino acid ~ DIFFERENT CODONS CODE FOR DIFFERENT AMINO ACIDS!!!

  24. Transcription Process by which genetic information encoded in DNA is copied onto messenger RNA Occurs in the nucleus DNA mRNA Translation Process by which information encoded in mRNA is used to assemble a protein at a ribosome Occurs on a Ribosome mRNA protein Transcription vs. Translation Review

  25. Protein Synthesis Visual Summary

  26. Protein Synthesis Video Summary http://videos.howstuffworks.com/hsw/12588-the-science-of-life-rna-and-protein-synthesis-video.htm

  27. Errors in Replication • Mutations are heritable changes in DNA, which can be passed on to future generations. They can occur in any gene and randomly. • Nondisjunction • Any one gene has a one in a million chance to be mutated. We have so many genes that mutations are fairly common. Each of us carries several mutations in our bodies. • Causes may include radiation and exposure to chemicals, viruses… • Mutations can be: • Useful (positive) • Harmful (negative) • No effect (neutral)

  28. Chromosomal Alterations/mutations: Gross alterations that affect the structure and/or the number of chromosomes. These include: • Translocation • Nondisjunction: chromatids fail to split at centromere (Turner’s syndrome) c) Duplication d) Inversion e) Deletion

  29. POINT MUTATIONS Changes in one or two bases Point mutations can be divided into 2 general categories: base-pair substitutions and base-pair insertions or deletions (frameshift mutations)

  30. Base Substitutions: Involves a change in one of the bases. These could be: • Silent: no effect, codes for the same amino acid • Missense: altered amino acid sequence, varying severity (sickle-cell, colourblindness, hemophilia)  translations will be terminated prematurely • Chain Termination/ Nonsense: produces a stop codon and stops production of protein  leads to non-functioning proteins

  31. Frameshift Mutation: Addition or deletion of bases; codons are shifted out of place

  32. DNA Mutation Problem Set Given the following sequence, what would happen if… DNA: TATATTAGAGGCTCATAT1CTTCCTACG2TTCTAGAT3GTTCTC4ATT mRNA: _______________________________ a.a.’s: ________________________________ Use a separate sheet of paper to solve this problem. Write out the entire mRNA sequence, then the entire sequence of amino acids starting with the start codon. Then replace the bases as indicated and figure out what kind of mutation will occur with each substitution or deletion/insertion. a)Replace T3 with A b) Replace GT with CA c) Replace G2 with A d) A inserted after T1 e) Remove C4

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