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DNA - PowerPoint PPT Presentation


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DNA. Deoxyribonucleic Acid. Defined : Molecule that stores genetic information Monomer: Nucleotide Millions of nucleotides bond to make nucleic acids Gene: section of DNA that holds instructions to build a protein. Nucleotide Structure. A. T. Three parts Sugar molecule Phosphate group

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Presentation Transcript
slide2

Deoxyribonucleic Acid

  • Defined: Molecule that stores genetic information
  • Monomer: Nucleotide
  • Millions of nucleotides bond to make nucleic acids
  • Gene: section of DNA that holds instructions to build a protein
nucleotide structure
NucleotideStructure

A

T

  • Three parts
    • Sugar molecule
    • Phosphate group
    • Nitrogen base

(A, T, C, or G)

  • Nucleotides combine to make nucleic acids
  • A pairs with T
  • C pairs with G

G

C

G

C

C

G

T

A

slide4

How many

Nucleotides?

slide5

Nucleotides

  • Sugar (Deoxyribose) connects with the phosphate group
  • 4 Different Bases:
    • Adenine (A)
    • Thymine (T)
    • Guanine (G)
    • Cytosine (C)
  • Chargaff’s Rules:
    • Rule: amount of A = amount of T
    • Rule: amount of C = amount of G
  • Human DNA: ~3 billion pairs

C

T

A

A

T

G

T

slide6

Double Helix

  • James Watson and Francis Crick identified DNA’s structure in 1953
  • Double Helix: spiral shape of DNA
  • Nucleotide strands are connected by a hydrogen bond
slide7

DNA Replication

  • Defined: Process of copying DNA
    • During interphase (S-stage)
  • Step 1: DNA Helicase “unzips” the two DNA strands (breaks the H bonds)
  • Step 2: Free floating nucleotides (A, T, C, G) match up
  • Step 3: DNA Polymerase reconnects the two strands
slide8

DNA

polymerase

Step 1:

DNA Helicase “unzips” the two DNA strands (breaks the H bonds)

T

A

A

T

Both DNA molecules are identical

Both DNA molecules contain one original strand and one new strand.

This is called the:

semiconservative model

G

C

G

C

A

T

C

G

Step 2:

Free floating nucleotides (A, T, C, G) match up

T

A

A

T

G

C

G

C

Step 3:

DNA Polymerase reconnects the two strands

C

G

T

A

C

G

A

T

DNA Polymerase

DNA

Helicase

slide10

Accuracy & Repair

A

T

T

A

  • Mutation: change in DNA sequence
  • Mutations can be corrected
    • Enzyme “proofreads” DNA and check/correct errors
  • Pre-repair: 1 in 10,000 nucleotides has an error
  • Post-repair: 1 in 1 billion nucleotides has an error

T

A

C

G

enzyme

A

C

T

C

G

G

C

review
Review
  • Name the three parts of a DNA nucleotide.
  • Name the four nitrogen bases.
  • List Chargaff’s rules.
  • Fill in the missing DNA nucleotides:

A C ? T ? ? ? G C T ? ? A ? C ? T T

? ? C ? T A T ? ? ? C A ? G ? G ? ?

  • List what takes place during the three stages of DNA replication.
  • What type of organic moleules are DNA helicase and DNA polymerase?
  • Why is DNA replication considered semiconservative?
  • Where is the DNA mutation?

T A G G C C T G T C G A A C A G T

A T C C G G A C A A C T T G T C A