introduction to dna d eoxyribo n ucleic a cid
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Introduction to DNA ( D eoxyribo n ucleic a cid). What do you know?. Scientists. Phoebus Levene. 1920 – Determined the basic structure of nucleotides that make up DNA 5-carbon sugar, phosphate group, and a nitrogenous base. Erwin Chargaff. 1952 - Nitrogenous base composition

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phoebus levene
Phoebus Levene
  • 1920 – Determined the basic structure of nucleotides that make up DNA
  • 5-carbon sugar, phosphate group, and a nitrogenous base
erwin chargaff
Erwin Chargaff
  • 1952 - Nitrogenous base composition
  • % of adenine is equal to % of thymine
  • % of guanine is equal to % cytosine
  • Composition of DNA varies from species to species
maurice wilkins and rosalind franklin
Maurice Wilkins and Rosalind Franklin
  • 1951 - Worked with a technique called X-ray diffraction
  • Determined the helical nature of DNA
james watson and francis crick

A

James Watson and Francis Crick
  • 1953 – Determined the structure of DNA using Chargaff’s and Franklin’s data
dna d eoxyribo n ucleic a cid
DNA (Deoxyribonucleic acid)
  • Nucleic acid
  • Consists of monomers called nucleotides
  • Stores genetic information, determines an organisms traits by synthesizing proteins
  • Each organisms genome is unique
structure of dna1
Structure of DNA
  • Double helix
  • Consists of a double strand of nucleotides
  • Two strands are anti-parallel
    • 5’ to 3’
    • 3’ to 5’
nucleotide
Nucleotide
  • Three parts of a nucleotide
    • 5 carbon sugar called deoxyribose
    • Phosphate group
    • A single nitrogenous base
four nitrogenous bases
Four Nitrogenous Bases
  • Purines (double ring)
    • Adenine (A)
    • Guanine (G)
  • Pyrimidines (single ring)
    • Thymine (T)
    • Cytosine (C)
chargaff s rules
Chargaff’s Rules
  • A-T (2 hydrogen bonds)
  • C-G (3 hydrogen bonds)
slide17

Sides of molecule - Alternating sugars and phosphates held together by strong covalentbonds

  • Center – two nitrogenous bases held together by weak hydrogenbonds
dna structure

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DNA Structure
  • Click on the hyperlink above to watch a short animation about the structure of DNA
genes
Genes
  • The sequence of nucleotides in an organisms genome is unique
  • Genes consist of sequences of nucleotides
human genome
Human Genome
  • 3164.7 million nucleotides
  • Average gene length is 3000 base pairs
  • Largest gene is 2.4 million base pairs
  • Approximately 20,000 – 25,000 genes
why replicate
Why replicate?
  • Each new cell created through cell division must receive an exact copy of the original cells DNA
  • Occurs in the nucleus of cells
dna replication1

A

DNA Replication
  • Semi-conservative– new DNA molecules have one original template strand and one new strand
  • Follows complementarybasepairrules
  • “Leading strand” – continuously synthesized
  • “Lagging strand” – synthesized in fragments
steps of dna replication

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Steps of DNA Replication

1. DNAhelicaseunzips the original DNA molecules by severing hydrogen bonds between nucleotides

slide28

2. New nucleotides are added to the template strands using DNA polymeraseenzymes(complementary base pairing)

dna replication2

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DNA Replication

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

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