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Warm-up : 4/4/11 Complimentary Strand

Warm-up : 4/4/11 Complimentary Strand. Do this on a separate sheet in your notebook. What pairs up with: Adenine? Guanine? For the following strands give the complimentary (other side of the double helix). Write out both. ATGCGTAAT GCGTTAACT. Sugar. What does DNA look like?.

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Warm-up : 4/4/11 Complimentary Strand

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  1. Warm-up : 4/4/11Complimentary Strand • Do this on a separate sheet in your notebook. • What pairs up with: • Adenine? • Guanine? • For the following strands give the complimentary (other side of the double helix). Write out both. • ATGCGTAAT • GCGTTAACT

  2. Sugar What does DNA look like? • DNA has.. • A sugar/phosphate backbone • 4 Chemical bases

  3. The bases • It is composed of 4 chemical bases: Adenosine (A), Thymine (T), Cytosine (C) and Guanine (G). • A always pairs with T • C always pairs with G • The pairs are held together by hydrogen bonds (WNC’s).

  4. What does DNA do? • DNA is the genetic code. • It determines our physical characteristics: from our hair color to what we are allergic to. • Our DNA codes for 20 amino acids which are the building blocks of life.

  5. What Is DNA Replication • DNA Replication is the process in which the DNA within a cell makes an exact copy of itself. • Why does DNA replicate? • During which phase of the cell cycle does DNA replicate?

  6. Steps of Replication • Unwind • Unzip • Insert • Proofread

  7. DNA Replication models

  8. The Three Possible DNA Replication Models • Conservative- would leave the original strand intact and copy it. • Dispersive-would produce two DNA molecule with sections of both old and new along each strand. • Semiconservative –would produce DNA molecule with both one old strand and one new strand.

  9. DNA replication • DNA replication: the DNA strand “unzips”, the weak hydrogen bond comes undone, and the base pairs separate

  10. Insert • After the DNA molecule opens up, new nucleotides are brought in and match up to their complimentary base. (A-T, C-G)

  11. DNA Replication Replication occurs during Interphase Replication fork Replication fork Replication bubble Hydrogen bond DNA replication is the process where an entire double-stranded DNA is copied to produce a second, identical DNA double helix.

  12. DNA Replication DNA helicase • Helicase unwinds the double helix starting at a replication bubble. • The two strands separate as the hydrogen bonds between base pairs are broken. • Two replication forks form and the DNA is unwound in opposite directions.

  13. DNA Replication • Helicase has completed unwinding the DNA strand. • Single strand Binding Proteins (SSB) keep the two strands from re-annealing (coming back together).

  14. DNA Replication Leading Strand Primase RNA Primer Lagging Strand • Primase is an RNA polymerase that makes the RNA primer. • These primers “tell” the DNA polymerase where to start copying the DNA.

  15. DNA Replication Leading Strand 5’ 3’ Direction of Replication DNA Polymerase 3’ 5’ Lagging Strand Direction of Replication • The DNA polymerase starts at the 3’ end of the RNA primer of the leading stand CONTINUOUSLY. • DNA is copied in 5’ to 3’ direction. • DNA polymerase copies the lagging strand DIS- continuously.

  16. DNA Replication • The dis-continuous pieces of DNA copied on the lagging strand are known as Okazaki fragments.

  17. DNA Replication Another DNA Polymerase removes the RNA primers and replaces them with DNA.

  18. DNA Replication ligase Finally the gaps in the sugar phosphate backbone are sealed by DNA ligase There are now 2 identical double helices of DNA.

  19. Proofread • The nucleus has enzymes that “read” through the molecule looking for mistakes. • If one is found, the molecule cuts out the incorrect nucleotide and replaces it. • Even with this molecule, sometimes a mistake is made, causing a change.

  20. Something old, Something new • The process is semi-conservative; each new molecule has one of the old strands and one of the new strands.

  21. DNA Video clip • http://bio-rad.cnpg.com/Video/flatFiles/799/ Remember that DNA is replicated using a series of enzymes. PCR= Polymerase Chain Reaction, lab procedure that makes several copies of a certain sequence of DNA, used to amplify a sequence so scientists have an easier time looking at it.

  22. Video Animations • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

  23. DNA Paper Model Must make sure you do questions 1 and 3 to be able to do homework. • Watson/Crick- double helix structure discovery • Hershey/Chase- confirmed that DNA was genetic material • Franklin/Wilkins- X-ray crystallography of DNA structure • Pauling/Chargaff- specific proportions of bases and that DNA was genetic material HW: Questions 1-10 Wednesday: Finish building model in class and create poster

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