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12.1 and 12.2 DNA and DNA Replication
DNA & DNA Replication
Nucleotides· monomers of DNA· 3 parts
5-carbon sugarphosphate groupnitrogen base
· 4 kindspyrimidines - cytosine (C), thymine (T)purines -
guanine (G), adenine (A)
· complementary base pairing· C = G and G = C· A = T and T = A·
base pairs are connected by hydrogen bonds (H-bonds)
Chargaff's Rule1 According to Chargaff's Rule, adenine
(A) always binds with...
A cytosine (C)
B thymine (T)
C guanine (G)
D adenine (A)
2 MATA: What are the 3 parts of a nucleotide?
A 5-carbon sugar
B hydrogen bond
C nitrogen base
D phosphate group
E sulfur group
X-ray evidence· Rosalind Franklin
X-ray diffraction· her work showed DNA was...
double strandednitrogen bases on the insidetwisted
· initially given no credit for her work
Click for video on Rosalind
Photo 51
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12.1 and 12.2 DNA and DNA Replication
structure of DNA· Watson and Crick's model - double helix·
complementary base pairs
A - T and C - G· base pairs connected by H-bonds· chains of
nucleotides
1 molecule of DNA contains millions of nucleotides· "sugar
phosphate backbone"
outside of DNA made of up sugars and phosphates
3 MATA: Which of the following describe the structure of
DNA?
A single helix
B C - G
C hydrogen bonds
D bases on the outside
E sugar-phosphate backbone
· making an exact copy of DNA· occurs during the S phase of
Interphase· base pairing makes it possible· occurs from 3' end to
5' end· controlled by enzymes· semi-conservative - DNA molecules
consist of 1 old and 1 new strand
Replication Steps of Replication1. helicase (enzyme) "unzips" a
molecule of DNA2. each strand serves as a template for the
attachment of complementary bases3. DNA polymerase (enzyme)
constructs new DNA strand and "proofreads"
Click for replication animation
A A T T C C G G A T C G
T T A A G G C C T A G Chelicase
DNA polymerase
DNA polymerase
PullPull
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12.1 and 12.2 DNA and DNA Replication
4 What enzyme is responsible for unzipping DNA?
A DNA polymerase
B DNA transcriptase
C RNA polymerase
D helicase
Replication Practice1. CCC GGG TTT AAA GCC ATA
2. TTG CAA GGC ATT CTG GAT
3. AGC CAG TTC GAG TCA CAT
5 Replicate the following strand of DNA.ATA CGA GAT TCC CTG
A ATA CGA GAT TCC CTG
B TAT CGA CTA TCC GAC
C TAT GCT CTA AGG GAC
D TAT GCT GTA AGG CAC