Physical Structure of the Gene---------------------Lecture 1
The Complementation Test and Gene Function-----Lecture 2
Mendelian Genetics-----------------------------------Lecture 3
Probability and Pedigrees-----------------------------Lecture 4
Chromosomes and Sex Linkage------------------------Lecture 5
, Physical Structure of the Gene
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.
, Transcription
Translation
Folded proteins:
enzymes
structural proteins
membrane channels
hormones
Gene: DNA segment needed to make a protein
Genes are typically 103 - 104 base pairs in size although they can be much larger. For
example, the human dystrophin gene is 2 x 106 base pairs.
E.coli has about 4,200 genes which isn’t very many considering that at least 1,000
different enzymes are needed carry out just the basic biochemical reactions in a cell.
The smallest genome for a free-living organism (i.e. a cell, not a virus) is that of the
bacterium Mycoplasma genetalium which encodes only 467 genes. Humans are at the
other end of the spectrum of complexity and have about 35,000 genes.
The Complementation Test and Gene Function-----Lecture 2
Mendelian Genetics-----------------------------------Lecture 3
Probability and Pedigrees-----------------------------Lecture 4
Chromosomes and Sex Linkage------------------------Lecture 5
, Physical Structure of the Gene
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.
, Transcription
Translation
Folded proteins:
enzymes
structural proteins
membrane channels
hormones
Gene: DNA segment needed to make a protein
Genes are typically 103 - 104 base pairs in size although they can be much larger. For
example, the human dystrophin gene is 2 x 106 base pairs.
E.coli has about 4,200 genes which isn’t very many considering that at least 1,000
different enzymes are needed carry out just the basic biochemical reactions in a cell.
The smallest genome for a free-living organism (i.e. a cell, not a virus) is that of the
bacterium Mycoplasma genetalium which encodes only 467 genes. Humans are at the
other end of the spectrum of complexity and have about 35,000 genes.
