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DNA Structure (12.1)
State Standards
2A. Distinguish between DNA and RNA.
2B. Explain the role of DNA in storing and transmitting cellular information.
Click on a lesson name to select.
Molecular Genetics
Genetics Genetics is the branch of biology that studies
heredity, the passing of traits (characteristics) from parents to offspring.
This passing oftraits involves the 2nucleic acids,DNA & RNA.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
Nucleic Acid Structure Nucleotides are the building blocks of DNA &
RNA
Nucleotides consist of a five-carbon sugar, a phosphate group, and a nitrogen-containing base
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
DNA Structure
The sugar found in DNA is called deoxyribose.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
DNA StructureCont’d The double helix
shape of DNA is often compared to a twisted ladder.
The ladder is made of 2 very long chains of nucleotides.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
DNA Structure Cont’d The rails of the ladder
are represented by the alternating deoxyribose and phosphate.
The pairs of bases
(cytosine–guanine or thymine–adenine) form the steps or rungs.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
The bases in a nucleic acid always pair up in the same way.
This is called Chargaff’s rule.
12.1 DNA: The Genetic Material
Chapter 12
Base Pairing
Molecular Genetics
Base Pairing Cont’d
12.1 DNA: The Genetic Material
Chapter 12
The 2 sides of the ladder are held together by hydrogen bonds.
Adenine always pairs with Thymine.
Guanine always pairs with Cytosine.
Molecular Genetics
The DNA Language12.1 DNA: The Genetic Material
Chapter 12
•DNA carries information in a triplet code.
•Each sequence of 3 nucleotides codes for a certain amino acid or for the beginning or end of a sequence.
•The genetic code is unique for each organism.
12.1 DNA: The Genetic Material
Molecular Genetics
Chromosome Structure
DNA coils around histones to form nucleosomes, which coil to form chromatin fibers.
The chromatin fibers supercoil to form chromosomes that are visible during cell division.
Chapter 12
1. A2. B3. C4. D
FQ 2
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Molecular GeneticsChapter 12
A. A—G and C—T
B. A—T and C—G
C. C—A and G—T
D. C—U and A—G
What is the base-pairing rule for purines and pyrimidines in the DNA molecule?
12.1 Formative Questions
1. A2. B3. C4. D
FQ 3
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Molecular GeneticsChapter 12
12.1 Formative Questions
A.chromatin and histones
B. DNA and protein
C. DNA and lipids
D. protein and centromeres
What are chromosomes composed of?
1. A2. B3. C4. D
CAQ 1
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Molecular GeneticsChapter 12
Look at the following figure. Identify the proteins that DNA first coils around.
Chapter Assessment Questions
A. chromatin fibers
B. chromosomes
C. histones
D. nucleosome
#14.
Use the analogy of a staircase or a railroad track to describe the structure of DNA.
