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DNA - double helix shape -like a winding staircase PowerPoint Presentation
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DNA - double helix shape -like a winding staircase

DNA - double helix shape -like a winding staircase

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DNA - double helix shape -like a winding staircase

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  1. DNA -double helix shape -like a winding staircase

  2. Composed of 4 bases • Guanine (G) • Cytosine (C) • Adenine (A) • Thymine (T) • Always bond together A-T C-G • Each base connected to the _______-_______ _________ • Nucleotide = 1 sugar + phosphate + base (like adenine)

  3. DNA is complementary • The sequence of bases on one strand determines the sequence of bases on the other. What is the complement to this single strand of DNA? Watson and Crick – 2 scientists that figured out the double helix shape of DNA. -(although they actually used the work of other scientists to figure it out)

  4. DNA Replication • When cells ________, DNA makes an exact ________ of itself. • DNA serves as a template (the parent).

  5. Enzymes involved • Remember enzymes are a type of ________ that help a reaction occur. • DNA Helicase • Enzyme that cuts open double stranded DNA . • Think scissors! • Makes a replication fork

  6. Enzymes II • Primer (put on by the enzyme primase) • Short sequence laid down that is starting point for DNA Polymerase • DNA Polymerase • Enzyme that helps add bases 1 by 1. • Makes new 2nd strand. • Can only add bases onto 3’ end • New strand made in 5’-3’ direction.

  7. DNA Replication 5’------------------3’ 3’------------------5’ • 5’ to 3’ during DNA replication as well.

  8. Okazaki Fragments make lagging strand

  9. Replication – Daughter DNA Creates an exact copy! Each new strand has one of the original strands in it. Meselson Stahl experiment proved this.

  10. AATGGCGAGCT TTACCGGTCGT What is wrong with the DNA on the left? Describe in your own words how the double strand of DNA on the left would make a copy of itself. Practice question

  11. http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swfhttp://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

  12. Notice how the only available place for the next nucleotide to bind is the oxygen off the 3rd carbon (3’ carbon). The 5’ carbon (the phosphate off it) from the nucleotide being added is connecting to the open 3’ end. All nucleotides are added to the 3’ end, thus Polymerase goes in the 5’- 3’ direction.

  13. RNA Structure • Serves as a messenger between the ______ and the ________. • Carries information in order to make _______ in the __________.

  14. RNA Structure • A= • G= • C= • U= • _______ replaces _______ • _______ stranded.

  15. Transcription Only the leading strand is read!

  16. Transcription Review Questions • 1. Describe 3 differences between RNA and DNA. • 2. Describe the process of transcription in your own words. • 3. What is the purpose of transcription? • 4.Transcribe the single strand of DNA below. ACCGTGTCGAATGC • 5. How might you compare the process of transcription and replication?