DNA DNA Deoxyribonucleic Acid a nucleic acid that

DNA • DNA (Deoxyribonucleic Acid) a nucleic acid that contains all of an individual’s genetic information. • Shape: Double helix ladder • Location: In the nucleus

DNA Parts: 1. Nitrogen bases: Pair up to form the rungs of the DNA twisted ladder. • • Adenine(A) Complementary Base Pairs Guanine(G) G–C Cytosine (C) A–T Thymine(T)

DNA • Gene: A specific DNA sequence that codes for one protein. • Chromosome: A molecule of DNA that is tightly coiled. – A bunch of genes makes up one chromosome – Humans have 46 chromosomes (23 pairs)

Protein Synthesis • One gene codes for one protein. • We say a gene is expressed when the protein it codes for is made.

Protein Synthesis There are two parts to Protein Synthesis: 1. Transcription (DNA m. RNA) 2. Translation (m. RNA protein) Protein Synthesis Requires: 1. m. RNA (a single stranded copy of DNA) 2. ribosome (organelle that builds proteins) 3. amino acids (building blocks of proteins)

Transcription: Process in which a sequence of DNA is copied into a sequence of m. RNA. • Location: Occurs in the nucleus. Why does it occur? The information in DNA needs to get out to the cell, but the DNA wouldn’t be safe leaving the nucleus

Translation: Process in which the m. RNA sequence gets “translated” to FORM PROTEINS. Location: Occurs on ribosomes outside the nucleus.

How Does Translation Occur? 1. m. RNA leaves the nucleus and attaches to a ribosome 2. Ribosome “reads” the m. RNA and attaches the correct amino acid for each codon Codon – 3 nucleotide sequence 3. Once the entire m. RNA strand is translated, the newly made chain of amino acids forms a protein

Amino Acids Building blocks of proteins – the cell makes different proteins by combining amino acids differently There are 20 different Amino Acids 12 can be made by your body 8 must be ingested (Essential Amino Acids)

Gene Mutations • Gene Mutation: –a random change in the nucleotide sequence of DNA

Gene Mutations • Point Mutation – Affects a single nucleotide, usually by substituting one nucleotide for another

Types of Point Mutations • Silent – Nucleotide changes, but amino acid doesn’t • Missense – Nucleotide change causes an amino acid to change • Nonsense Mutation – Nucleotide change creates/destroys a start or stop codon (ribosome doesn’t know when to start/stop translating)

Gene Mutations • Frame Shift Mutation – Inserts or deletes nucleotide so the “reading” frame is shifted • Every single codon changes

• In a deletion, a single base is deleted and the reading frame is shifted.

Effect of Gene Mutations • Mutations can cause a change in the proteins a cell makes. • Mutations can be harmful, beneficial, or have no effect at all.