Introduction to Genetics: DNA

Grades 9-12

Matt Cardinal

Where is DNA?• Most Organisms in the world have DNA

• It plays an important role on the function of an organism

• DNA is found in cells and all animals are made up of cells

• DNA is located in the nucleus of a cell

Structure of DNA• James Watson and Francis Crick – 1953

• Double Helix shape– Allows it to be easily opened and closed

• Composed of nucleotide bases, sugars, and phosphates

• Four bases are: adenine, cytosine, thymine, and guanine

• Adenine and Thymine pair together

• Cytosine and Guanine pair together

Functions of DNA

• Requires enzymes, proteins, and other chemicals

• Replication – making copies

• Protein synthesis – creation of molecules

• Regulation

Replication

• Nuclear enzymes help break the bonds between the nucleotide bases

• Unwinds DNA

• Copying of DNA is required for mitosis and meiosis

DNA Replication

Protein Synthesis

• Process by which proteins are produced

• Proteins is a string of amino acids

• Code is three nucleotide bases long called triplets

• 64 possible three-letter combinations but only 20 possible amino acids

• Some are start and stop amino acids

Protein Synthesis: Transcription

• Copying the DNA message to RNA

• Message transcribed onto RNA

• mRNA takes message from the DNA

• Instead of thymine, RNA uses uracil

• The triplets transcribed onto RNA are called codons

Protein Synthesis: Translation

• Chemical signals initiate translation

• Translation is the process of converting the mRNA message into a protein

• tRNA brings amino acids to the ribosome

• Create bonds between amino acids

• Result is a string of amino acids

• Folding occurs to produce a protein

Regulation

• Error rate of 1 in 10 billion

• Monitoring system – aligns enzymes with bases

• Proofreading system – examines the nucleotides

• Repair system – repairs the segment

• Repair mechanism – repairs damage from external sources

Summary

• DNA replication, protein synthesis, and regulation are important for everyday life. Without it, life would not exist.

• DNA is a major part of heredity. Each individual has unique DNA that is received from the parents