3. What is DNA and how does it code for different traits?

4. DNA Structure DNA: deoxyribose nucleic acid
One of the 4 macromolecules (nucleic acid)
Polymer of nucleotides

5. DNA Structure

6. Nucleotide: subunits of nucleic acids

7. Nucleotides are made up of 3 major parts:
Phosphate group
Nitrogenous base
5 carbon sugar

8. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
DNA Structure
Nucleotides
Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base

9. DNA is made up of 4 different nitrogenous bases:
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)

10. Purine bases: A and G
Pyrimidine bases: C and T

11. Chargaff’s Rule: A always bonds with T and G always bonds with C

12. Weak hydrogen bonds hold bases together

13. Chargaff’s rule: C = G and T = A
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Chargaff
Chargaff’s rule: C = G and T = A

14. What do you notice about different species’ nucleotides?

15. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
When the nucleotides bond together, DNA forms a double helix

16. DNA Structure DNA looks like a twisted ladder
Sides of the ladder —alternating deoxyribose (sugar) and phosphate groups
Steps of the ladder —complimentary nitrogenous bases (cytosine–guanine or thymine–adenine)

17. Two scientists, Watson and Crick, are credited with building the double helix model

18. two outside strands consist of alternating deoxyribose and phosphate
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Watson and Crick
Built a model of the double helix that conformed to the others’ research
two outside strands consist of alternating
deoxyribose and phosphate
cytosine and guanine bases pair to each
other by three hydrogen bonds
thymine and adenine bases pair to each
other by two hydrogen bonds

19. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Chromosome Structure
DNA coils around histones (proteins) to form nucleosomes
Nucleosomes package and fold the DNA into chromatin fibers
The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis

21. Semiconservative Replication
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Semiconservative Replication
Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and
one strand of new DNA.

22. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Unwinding
An enzyme, DNA helicase, is responsible for unwinding and unzipping the double helix.

23. Bases are exposed
“Free” nucleotides found in the nucleus bond to their complimentary bases of both strands (A to T and C to G)
Two new identical molecules of DNA are formed

24. Each new cell gets a copy of the DNA

25. This occurs during interphase!!

26. DNA polymerase (an enzyme) attaches nucleotides to the leading strand
Chapter 12
Molecular Genetics
12.2 Replication of DNA
One strand is called the leading strand and is elongated as the DNA unwinds.
DNA polymerase (an enzyme) attaches nucleotides to the leading strand
The other strand of DNA, called the lagging strand, elongates away from the replication fork.