The Quick and Dirty Review of DNA

Deoxyribonucleic Acid DNA is composed of subunits called nucleotide. A DNA nucleotide has three parts: Phosphate 5-Carbon Sugar Nitrogenous Base Adenine Thyamine Guanine Cytosine

Structure Double Helix (aka The twisted ladder) Rungs= Bases Sides= alternating phosphates and sugars. Hydrogen bonds hold the 2 strands together Follows base pairing rules: A – T C-G

Replication Goal is to make exact copy of DNA. In summary, the DNA unwinds and separates. Enzymes read one side and make a complimentary sequence using free nucleotides. The same process happens on the other side.

Using DNA The information in DNA is used to make proteins.

DNA vs. RNA

The Steps to Make a Protein Transcription Occurs in the nucleus Translation Occurs at the ribosome

Transcription (DNA  mRNA) DNA pulls apart RNA polymerase make a complimentary mRNA sequence to one side of the DNA molecule. Once entire gene is copied, DNA strands bond back together and mRNA goes off to the ribosome.

Translation (mRNA  Protein) mRNA binds to ribosome. Ribosome starts reading at the start codon AUG tRNA’s bring the amino acid over to the ribosome. The process continues until a stop codon has been reached.

Example Problem DNA: TACGGTACGCTG mRNA: AUG-CCA-UGC-GAC Protein: Methionine-Proline- cysteine-aspartate

Mutations Chromosomal Mutations Large amount of DNA are effected. Gene mutations Only affects a one or a few nucleotides Also called point mutations Deletions/Insertions Substitutions Mutation may cause different outcome Frameshift Many amino acids are wrong Early Stop Incomplete protein Silent No Change in the protien Missense 1 amino acid is different Chromosomal Mutations Large amount of DNA are effected. Inversion Translocations Large scale addition/deletions Duplications Many genes are messed up