2. 2A. Distinguish between DNA and RNA.
DNA Structure (12.1)
State Standards
2A. Distinguish between DNA and RNA.
2B. Explain the role of DNA in storing and transmitting cellular information.

3. Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Genetics
Genetics is the branch of biology that studies heredity, the passing of traits (characteristics) from parents to offspring.
This passing of
traits involves the 2
nucleic acids,
DNA & RNA.

4. Nucleic Acid Structure
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
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

5. The sugar found in DNA is called deoxyribose.
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
DNA Structure
The sugar found in DNA is called deoxyribose.

6. The double helix shape of DNA is often compared to a twisted ladder.
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
DNA Structure
Cont’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.

7. Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
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.

8. The bases in a nucleic acid always pair up in the same way.
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Base Pairing
The bases in a nucleic acid always pair up in the same way.
This is called Chargaff’s rule.

9. Adenine always pairs with Thymine.
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Base Pairing Cont’d
Adenine always pairs with Thymine.
Guanine always pairs with Cytosine.
The 2 sides of the ladder are held together by hydrogen bonds.

10. DNA carries information in a triplet code.
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
The DNA Language
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.

11. Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
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.

12. What is the base-pairing rule for purines
Chapter 12
Molecular Genetics
12.1 Formative Questions
What is the base-pairing rule for purines
and pyrimidines in the DNA molecule?
A—G and C—T
A—T and C—G
C—A and G—T
C—U and A—G A B C D
FQ 2

13. What are chromosomes composed of?
Chapter 12
Molecular Genetics
12.1 Formative Questions
What are chromosomes composed of?
chromatin and histones
DNA and protein
DNA and lipids
protein and centromeres A B C D
FQ 3

14. chromatin fibers chromosomes histones nucleosome
Chapter 12
Molecular Genetics
Chapter Assessment Questions
Look at the following figure. Identify the proteins that DNA first coils around.
chromatin fibers
chromosomes
histones
nucleosome A B C D
CAQ 1

15. #14.
Use the analogy of a staircase or a railroad track to describe the structure of DNA.