Chapter 13 packet: DNA and Protein Synthesis Part I

Genes – the instructions for inherited traits Genes are made of DNA, short for Deoxyribonucleic acid

Discovery of the structure of DNA DNA is in the shape of a double helix – discovered by Franklin & Wilkins through X-ray diffraction of DNA (a) 1953 - Watson & Crick used above information to construct 1st model of DNA (b)

Structure of DNA DNA is a made of nucleotides Nucleotides are composed of: Phosphate 5-carbon sugar (deoxyribose) 1 of 4 nitrogen-containing bases - adenine (A), thymine (T), guanine (G), or cytosine (C)

Hydrogen bonds – holds 2 strands of nucleotides together Shape: double helix (Two strands twist around each other) Base pairing: A & T C & G (complementary base pairs)

DNA Replication Purpose: makes an exact copy of DNA before the cell divides; ensures that each new cell gets a complete copy of the DNA DNA DNA DNA Replication Cell Division DNA

Steps: Unwinding and separating DNA strands Adding complementary bases If parent strand has A  T is added If parent strand has T  a is added If parent strand has C  G is added If parent strand has G  C is added Formation of two identical DNA molecules

Overview of DNA replication

Ladder configuration and DNA replication

Website showing animation: Each old strand (parent strand) of nucleotides serves as a template for each new strand (daughter strand). Proofreading and repair limits error rate to less than 1 per billion nucleotides. Website showing animation: http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf Video clip from class: http://www.youtube.com/watch?v=4jtmOZaIvS0

Enzymes involved in replication: DNA Helicase – breaks the hydrogen bonds between base pairs during replication DNA polymerase – adds new nucleotides to parent strand of DNA