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13.2 DNA Structure13.2 DNA Structure
What does DNA stand for?Deoxyribonucleic acid
What does DNA stand for?Deoxyribonucleic acid
DNAs Functions:DNAs Functions:
• Controls the production of proteins
• Can copy itself for new cells• Carries genetic information from one generation to the next
• Controls the production of proteins
• Can copy itself for new cells• Carries genetic information from one generation to the next
replication
transcription processing translation
II. Structure of DNAII. Structure of DNA
• Monomer of DNA= nucleotide• DNA is made of 2 chains of nucleotides.
• 3 parts of a nucleotide:– Pentose (5C) sugar= deoxyribose– Phosphate group– Nitrogen base
• Monomer of DNA= nucleotide• DNA is made of 2 chains of nucleotides.
• 3 parts of a nucleotide:– Pentose (5C) sugar= deoxyribose– Phosphate group– Nitrogen base
Bases in DNA
purines
pyrimidines
adenine
guanine
cytosine
thymine
N9
N1
• The nucleotides are joined in a chain; each nucleotide joined to the next by a covalent bond between the sugar and phosphate.
• Therefore the DNA molecule has a direction to it.
• The nucleotides are joined in a chain; each nucleotide joined to the next by a covalent bond between the sugar and phosphate.
• Therefore the DNA molecule has a direction to it.
• Due to Rosalind Franklin’s x-ray diffraction work, Watson and Crick knew that DNA was a helix.
• Due to Rosalind Franklin’s x-ray diffraction work, Watson and Crick knew that DNA was a helix.
• Watson and Crick realized in 1953 that the DNA molecule is composed of two strands running in opposite directions= antiparallel
• Watson and Crick realized in 1953 that the DNA molecule is composed of two strands running in opposite directions= antiparallel
Double helixDouble helix
• The two strands are linked in the center by hydrogen bonds.
• The two strands are linked in the center by hydrogen bonds.
“Chargaff’s rules”“Chargaff’s rules”
• 1950• Determined that the amount of:– Adenine=Thymine– Cytosine=Guaninein DNA.
• 1950• Determined that the amount of:– Adenine=Thymine– Cytosine=Guaninein DNA.
• Watson and Crick deduced that A must pair with T and G with C
=complimentary pairs
• Watson and Crick deduced that A must pair with T and G with C
=complimentary pairs
What about the structure of DNA varies from one
individual to the next?
What about the structure of DNA varies from one
individual to the next?
The sequence of nitrogen bases
The sequence of nitrogen bases