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DNA

DNA. DNA stands for deoxyribonucleic acid Basically it is the blueprints or genetic code that tells the cell what to do and how to do it Def: DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

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DNA

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  1. DNA • DNA stands for deoxyribonucleic acid • Basically it is the blueprints or genetic code that tells the cell what to do and how to do it • Def: DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

  2. What evidence supports the presence of some sort of genetic code? • Organisms have offspring that look like themselves

  3. Who discovered DNA? • Gregor Mendel, discovered the idea of a passing on of traits from one generation to the next. • But is was James Watson and Francis Crick who figured out the structure of DNA in the 1950’s.

  4. DNA Functions: • Store information: which controls the development and activities of cells/organisms • Replication: transmits information to the next cell/generation • Mutations: provides raw material for evolution.

  5. What are the components that make up DNA? • The parts of a DNA nucleotide are: • a 5 carbon sugar -deoxyribose • a phosphate group • nitrogenous base • The different nitrogenous bases are: • Adenine (A) • Thymine (T) • Guanine (G) • Cytosine (C)

  6. Certain Bases go Together • This is known as complementary base pairing: • Guanine (G) and Cytosine (C) (three bonds) • Adenine (A) and Thymine (T) (two bonds) • They are held together by HYDROGEN bonds • Only these combination of pairs of bases are capable of forming bonds

  7. Nitrogenous bases: • The purines: double rings • Adenine (A) • Guanine (G) • The pyrimidines: single ring • Thymine (T) • Cytosine (C)

  8. Sugar phosphate backbone: • Nucleotides are linked together by covalent bonds joining the 3’ carbon of one sugar to the 5’ phosphate of the adjacent sugar. • Draw diagram

  9. Each DNA molecule is made up of two polynucleotide strands arranged in a coiled double helix.

  10. Once the nitrogen bases have joined together the two strands of DNA are twisted like two strands of rope –forming a Double Helix. What do the structures of DNA look like?

  11. What would the other side of this DNA strand look like? • ATTGTGCCTATGATCA • TAACACGGATACTAGT • GGCTAATGCATGTAC • CCGATTACGTACATG

  12. DNA REPLICATION: • Is complex • Extremely rapid • Very accurate, only one in a billion are incorrectly paired. • Requires the cooperation of over a dozen different enzymes.

  13. DNA replication • Is semi-conservative: each double strand contains an “old strand and a newly synthesized strand. • Result: two DNA double helicies, each identical to the original one and each having one original strand from the parent DNA and one newly made complementary strand.

  14. Three steps of DNA replication: • P467 in text book

  15. The three steps of the semi-conservative replication of DNA: • Unzipping: the DNA double helix unwinds, and the two strands of DNA separate. DNA helicase helps the Hydrogen bonds to break.

  16. The three steps of the semi-conservative replication of DNA: 2. Complimentary Base Pairing: new nucleotides move in or pair up with bases of each template strand of DNA. These new nucleotides are always floating around within the nucleoplasm. • DNA polymerase helps with this

  17. The three steps of the semi-conservative replication of DNA: • Joining of adjacent nucleotides: after DNA polymerase has checked for errors, sugar-phosphate bonds form between adjacent nucleotides of the new strand. The new molecule winds into a doubles helix.

  18. Differentiate between the roles of helicase and DNA polymerase in DNA replication.

  19. Why does DNA replication happen? • So that when a cell divides the resulting daughter cells will both have all of the necessary instructions for proper functioning.

  20. What is the site of DNA replication with in the cell? Inside the nucleus. • Rate of DNA repliction: • 400 bases/sec with 1 error per 109 bases • Check out this amazing video of a website: http://www.dnai.org/lesson/go/19436

  21. Protein Synthesis • Can be broken down into the following basics: DNA → mRNA → Protein Transcription Translation

  22. Protein Synthesis • Unzipping: The DNA double helix unwinds to expose a sequence of nitrogenous bases. 2. Transcription: A copy of one of the strands is made. The copy is made of messenger ribonucleic acid (mRNA) which, following transcription, travels out of the nucleus into the main body of the cell, where protein synthesis occurs. 3. Translation: The mRNA couples with the protein synthesis apparatus (the ribosome). Then another type of RNA, known as transfer RNA (tRNA), brings free amino acids to the ribosome (initiation). 4.The anticodon present on the tRNA recognises the codon present on the mRNA, and the ribosome adds the amino acid to the growing chain of linked amino acids (polypeptides), cleaving it away from the tRNA (elongation). 5. As the polypeptide chain grows, it folds to form a protein. This continues until a stop codon is encountered and when this happens, the ribosome releases the polypeptide (termination).

  23. Determine the sequence of amino acids coded for by a specific DNA sequence • DNA: CGGTAATTCGACTCG • mRNA: • Amino Acids:

  24. mRNA codon vs tRNA anti-codon • An mRNA codon is three bases long • An tRNA anti-codon is also three bases long and contains the complementary base pairs for the mRNA codon. • So if the mRNA codon is AUG, what is the tRNA anti-codon? • UAC • But what amino acid is brought? • Methionine (met)

  25. Codons vs anticodons • DNA: TACCGGTTAGCG • mRNA: (codon) • tRNA: (anticodon) • Amino acids

  26. Mutations: • The source of mutations is DNA. • Sometimes in the copying of DNA there is a mistake made: • A nucleotide is omitted • A nucleotide is incorrectly paired. • Where the mistake happens determines the severity of the mutation

  27. Lets look at the following sentence: • THECATSATALLDAY • What happens if we change one letter? • THEBATSATALLDAY • What happens if we remove one letter? • HECATSATALLDAY

  28. IF we use the last DNA strand, but remove the first nucleotide, how does that effect the aminoacid sequence? • DNA: GGTAATTCGACTCG • mRNA: • Amino acids:

  29. Recombinant DNA: • Definition: a segment of DNA that is constructed out of DNA from two sources. • It allows scientists to insert segments of DNA from one organism into the chromosomes of another. • This allows the cell to have a function that it did not have previously.

  30. Examples of recombinant DNA in action: • Insulin, growth hormone, antibodies and proteins for cancer treatment are mass produced using bacteria inserted with the appropriate DNA. • Bacteria with DNA inserted to metabolize oil, to aid in the cleanup of oil spills.

  31. Examples of recombinant DNA in action: 3. Cloning 4. Repairing of genetic errors in humans. Removing their cells, repairing and reinserting them. 5. Hybrid species of some food crops so that they are resistant to certain diseases and more tolerant to extreme environment conditions.

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