Mrs. Ragsdale Biology SL All About DNA!

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

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

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

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

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

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

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

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

Dna replication tutorial http://www.wiley.com/legacy/college/boyer/0470003790/animations/replication/replication.swf