DNA & Protein Synthesis                

Structure of DNA Double stranded helix Structure determined in 1953 by Watson and Crick. Composed of nucleotides.

Nucleotides Composed of sugar, phosphate, and nitrogen base Sugar-Phosphate Backbone Deoxyribose sugar Phosphate group

Nucleotides continued ... Nitrogen base Adenine Thymine Cytosine Guanine Weak hydrogen bonds hold nitrogen bases together Sequence of nucleotides determines genotype of organism. } pair } pair

DNA Replication Enzyme breaks hydrogen bonds that hold the nucleotides together DNA unzips. Free nucleotides pair with exposed nucleotides on both strands.

Animation http://www.stolaf.edu/people/giannini/biological%20anamations.html

DNA Replication T-A-C-A-C-G Complementary strand?

From DNA to Protein ...

X X X X

Genes and Proteins RNA: helper DNA DNA determines your: amino acid sequenceprotein production. RNA: helper DNA Single strand Ribose sugar, not deoxyribose sugar. Uracil (nitrogen base) replaces Thymine of DNA, bonding with Adenine

mRNA 3 Types of RNA “WORKERS” Messenger RNA (mRNA): carries genetic info. from nucleus to cytoplasm Ribosomal RNA (rRNA): attach to mRNA; assemble the amino acids in order. Transfer RNA (tRNA): transfers amino acids to the ribosome to be assembled into protein.

Step 1: Transcription DNA making a mRNA in the nucleus so genetic message can get to cytoplasm

Animation http://www.stolaf.edu/people/giannini/biological%20anamations.html

Step 2: Translation: 1. Changes mRNA message to amino acids 2 Step 2: Translation: 1. Changes mRNA message to amino acids 2. Amino acids form a protein - tRNA carrying an amino acid, binds to mRNA.

Translation

Translation

The Genetic Code Proteins determine ALL of your characteristics!!! U Protein = Amino Acid + Amino Acid + Amino Acid + … There are 20 amino acids = “gazillion” proteins. Each set of 3 nitrogen bases forms a triplet, called a codon on mRNA called an anticodon on tRNA Start and Stop: AUG is the start codon. UAA, UGA, UAG are the stop codons. U A G

Genetic Code

Animation http://www.stolaf.edu/people/giannini/biological%20anamations.html

Genetic Changes ...

Mutation: A Change in DNA Simple error environmental chemical or radiation Can happen in all cells                                              Melanoma

Two types of gene mutations: Point mutation change in a single nitrogen base pair in DNA Results in the change of one amino acid of a protein. Frameshift mutation – One nitrogen base is added or deleted results in a drastic change in the amino acid sequence.

Point & Frameshift Mutations

Types of Mutations

Chromosomal Mutations Nondisjunction - organism has one more or one less chromosome than it should. Piece of chromosome could break away and become lost, or it could rejoin upside down.

Causes of Mutations Mutagens - agent that causes change in DNA. Radiation - x-rays, ultraviolet nuclear Chemicals - asbestos formaldehyde tobacco

Repairing DNA Often occurs naturally by the enzymes of the organism. However, if the exposure to the mutagen is very high, the chance for repair is slim.