1. Mrs. Ragsdale Biology SL
All About DNA!

2. The basic structure of dna
Nucleotides – the subunits of DNA
Monomers
Consist of: phosphate, 5-carbon sugar (deoxyribose) and nitrogen base

3. The 4 nucleotides
A – Adenine G - Guanine
T – Thyamine C – Cytosine

4. Monomers into polymers
Nucleotides are linked together with covalent bonds
Sugar of one nucleotide links to the phosphate of another nucleotide

5. Structure of DNA DNA is Double stranded Nucleotides pair up:
Complementary Base Pairing:
Adenine – Thymine
Cytosine - Guanine
Hydrogen Bonds form between the base pairs

6. DNA and Chromosomes DNA is very long for its size
DNA must be kept organized
Long thread don’t want tangles & knots
Histones – proteins that DNA wrap around
Acts like a spool for thread. (Keeps it organized)
Nucleosome- DNA wrapped around eight histone protein molecules and held together by another histone
Chromatin- DNA plus histones in eukaryotic cells

8. DNA Replication
Stage 1
The DNA double helix is unwound and separated into strands by breaking hydrogen bonds
DNA Helicase is the enzyme responsible for unzipping the DNA

9. Single strands act as templates for new strands
Stage 2
Single strands act as templates for new strands
DNA replication is semi-conservative because the “new” strand is half new half old
DNA Polymerase
Key enzyme in DNA replication
Attaches nucleotides to the growing new DNA strand

10. Stage 3
The daughter DNA molecule rewinds back into a double helix

11. Dna replication tutorial