Genetic Structure and expression – introduction to genetic
engineering
Genes
- What are they, where are they
- Central Dogma – transcription and translation
- In eukaryotes the coding region of a gene is often broken up by introns
- These introns are removed in the nucleus when mRNA is processed
- Only exons actually code for proteins – prokaryotic genes don’t usually have
introns
Mitochondria
Although most of our DNA resides in
chromosomes in the nucleus of the cell, there
are structures in the cytoplasm of
eukaryotes, called mitochondria that have
their own DNA
These mitochondria are the cells power
stations
Cells contain between 200 – 100, 000
mitochondria
Mitochondrial DNA – Mitochondrial DNA,
unlike nuclear DNA, is naked (ie. it is not
associated with histones or other proteins)
and circular
Mitochondrial DNA is very gene rich and
contains very little “junk” DNA
Mitochondrial DNA has a higher mutation rate than nuclear DNA
Mitochondrial DNA inheritance – found in males and females: because sperm
does not contribute its mitochondria to the fertilised egg we only inherit our
mothers mitochondrial DNA
Can be used to investigate female-specific migration history
Genetic Engineering
- Definition?
- Natural Events which alter or Rearragnge DNA sequences
- Mutations
- Viral Infection
- Bacterial Infection
, - Transposons, insertion sequences
- DNA uptake (transformation or conjugation) and recombination (eg. Bacteria and
fungi)
- Meiosis (sex)
Recombinant DNA technology allows you to:
- Isolate a specific gene
- Amplify to manageable amounts
- “Immortalise” by cloning (plasmids etc.)
- Read DNA sequence
- Manipulate (make specific changes, join to other DNA sequences)
- Insert into another organism (eg. Human gene expressed in goat’s milk)
Theoretical considerations in gene manipulations
- Do all organisms use DNA as the genetic material: yes , except some viruses
- Is DNA chemically identical in all species? No – methylation in most eukaryotes –
different in different species
- Is he genetic code universal? – Almost – minor differences in mtDNA of some
species
- Do all species use the same complement of amino acids? Yes.
- Are DNA control sequences the same? – No. Determined by the proteins present
– also tissue specific
Theoretical consideration s in gene manipulation
- Can DNA sequences be determined? – Yes: but only <1000 base pairs at a time
- Can DNA be cut and joined in a precise way? Yes – restriction endonucleases and
ligases
- Can DNA be synthesised in vitro? Yes – but only up to - 10, 000 base pairs
- Can DNA be replicated in vitro: Yes: PCR, cloning
Applications of DNA technology
1. Basic knowledge of biology:
- DNA and protein sequences
- Overexpression and characterisation of proteins
- Analysis of gene structure, expression, control
- “Reverse genetics” using deletion mutagenesis
- Site-directed mutagenesis
- Evolution, taxonomy, kinship
2. Production of proteins (industrial and therapeutic)
3. Diagnosis of disease
4. DNA profiling, forensics
5. Transgenic plants/animals (increase yield, resistance to pests/disease)
engineering
Genes
- What are they, where are they
- Central Dogma – transcription and translation
- In eukaryotes the coding region of a gene is often broken up by introns
- These introns are removed in the nucleus when mRNA is processed
- Only exons actually code for proteins – prokaryotic genes don’t usually have
introns
Mitochondria
Although most of our DNA resides in
chromosomes in the nucleus of the cell, there
are structures in the cytoplasm of
eukaryotes, called mitochondria that have
their own DNA
These mitochondria are the cells power
stations
Cells contain between 200 – 100, 000
mitochondria
Mitochondrial DNA – Mitochondrial DNA,
unlike nuclear DNA, is naked (ie. it is not
associated with histones or other proteins)
and circular
Mitochondrial DNA is very gene rich and
contains very little “junk” DNA
Mitochondrial DNA has a higher mutation rate than nuclear DNA
Mitochondrial DNA inheritance – found in males and females: because sperm
does not contribute its mitochondria to the fertilised egg we only inherit our
mothers mitochondrial DNA
Can be used to investigate female-specific migration history
Genetic Engineering
- Definition?
- Natural Events which alter or Rearragnge DNA sequences
- Mutations
- Viral Infection
- Bacterial Infection
, - Transposons, insertion sequences
- DNA uptake (transformation or conjugation) and recombination (eg. Bacteria and
fungi)
- Meiosis (sex)
Recombinant DNA technology allows you to:
- Isolate a specific gene
- Amplify to manageable amounts
- “Immortalise” by cloning (plasmids etc.)
- Read DNA sequence
- Manipulate (make specific changes, join to other DNA sequences)
- Insert into another organism (eg. Human gene expressed in goat’s milk)
Theoretical considerations in gene manipulations
- Do all organisms use DNA as the genetic material: yes , except some viruses
- Is DNA chemically identical in all species? No – methylation in most eukaryotes –
different in different species
- Is he genetic code universal? – Almost – minor differences in mtDNA of some
species
- Do all species use the same complement of amino acids? Yes.
- Are DNA control sequences the same? – No. Determined by the proteins present
– also tissue specific
Theoretical consideration s in gene manipulation
- Can DNA sequences be determined? – Yes: but only <1000 base pairs at a time
- Can DNA be cut and joined in a precise way? Yes – restriction endonucleases and
ligases
- Can DNA be synthesised in vitro? Yes – but only up to - 10, 000 base pairs
- Can DNA be replicated in vitro: Yes: PCR, cloning
Applications of DNA technology
1. Basic knowledge of biology:
- DNA and protein sequences
- Overexpression and characterisation of proteins
- Analysis of gene structure, expression, control
- “Reverse genetics” using deletion mutagenesis
- Site-directed mutagenesis
- Evolution, taxonomy, kinship
2. Production of proteins (industrial and therapeutic)
3. Diagnosis of disease
4. DNA profiling, forensics
5. Transgenic plants/animals (increase yield, resistance to pests/disease)
