Genetics Lecture 1 We will begin this course with the question:What is a gene? This question will take us four lectures to answer because there are actually several different definitions that are appropriate in different contexts. We will start with a physical definition of the gene.Conceptually this is the simplest and it will give me an excuse to briefly review some of the molecular biology that you probably already know. Genes are made of DNA For this course we will mostly think of DNA as an information molecule not as a chemical substance. T A A T C In 1953,Watson and Crick deduced that the structure of DNA was a double helix.It was not the helical structure per se,but the discovery of complementary base pairing that revealed how information could be encoded in a molecule and how this information could be exactly duplicated each cell division.Replication. G ATC CTAG GAT C CTAG G AT C C TAG In order to extract information from the DNA,the cell again uses the complementary base-pairing to make a copy of the information copied onto an RNA molecule.This is known as Transcription.RNA is chemically less stable than DNA and mRNA can be thought of as a temporary copy of DNA's information.Genetics Lecture 1 We will begin this course with the question: What is a gene? This question will take us four lectures to answer because there are actually several different definitions that are appropriate in different contexts. We will start with a physical definition of the gene. Conceptually this is the simplest and it will give me an excuse to briefly review some of the molecular biology that you probably already know. Genes are made of DNA For this course we will mostly think of DNA as an information molecule not as a chemical substance. In 1953, Watson and Crick deduced that the structure of DNA was a double helix. It was not the helical structure per se, but the discovery of complementary base pairing that revealed how information could be encoded in a molecule and how this information could be exactly duplicated each cell division. Replication. In order to extract information from the DNA, the cell again uses the complementary base-pairing to make a copy of the information copied onto an RNA molecule. This is known as Transcription. RNA is chemically less stable than DNA and mRNA can be thought of as a temporary copy of DNA’s information