Sunday, 4 September y
The control of gene expression
Genetic Mutations
Enzyme responsible for checking the DNA sequence is correct
- DNA polymerase
Silent mutation
- a change in the nucleotide base sequence that has no effect on the amino acid
- so the same protein will be synthesised and the phenotype will be the same
Why do mutations in introns not have an impact on the protein
- the introns are non coding sections of DNA
- the introns are removed by spicing
- so the introns are not translated by the ribosomes
Nonsense mutation
- formation of a premature stop codon
- produces a shorter polypeptide chain
- change in the protein structure - results in a non-functional protein
Why do translocation mutations have a significant impact
- multiple genes are affected
- change in the base sequence of multiple genes
- Change in the tertiary structure of multiple proteins
How may a mutation spread
- founder effect
- interbreeding
- Migration
Carcinogens
X ray
- alters the DNA structure
Tobacco
- contains mutagenic agent (increase methylation of tumour suppressor genes)
1
, Sunday, 4 September y
- Results in a mutation
- mutation stops tumour suppressor gene
- results in uncontrolled cell division
Regulation of gene expression
Stem cells
A cell that can divide an unlimited number of cells
It is undifferentiated
It can differentiate into other cells
How do cells become specialised
- Transcription factors used to activate/deactivate genes
- mRNA transcribed Cells taken from an em-
bryo before first few cell from active genes
divisions
- mRNA used in transla- tion to make proteins
- Proteins give the cell a specific function Pluripotent
Embryonic vs induced pluripotent cells
Both Multipotent
- can differentiate into other cells Heart cells
- can divide indefinitely
- can prevent fatality
2
The control of gene expression
Genetic Mutations
Enzyme responsible for checking the DNA sequence is correct
- DNA polymerase
Silent mutation
- a change in the nucleotide base sequence that has no effect on the amino acid
- so the same protein will be synthesised and the phenotype will be the same
Why do mutations in introns not have an impact on the protein
- the introns are non coding sections of DNA
- the introns are removed by spicing
- so the introns are not translated by the ribosomes
Nonsense mutation
- formation of a premature stop codon
- produces a shorter polypeptide chain
- change in the protein structure - results in a non-functional protein
Why do translocation mutations have a significant impact
- multiple genes are affected
- change in the base sequence of multiple genes
- Change in the tertiary structure of multiple proteins
How may a mutation spread
- founder effect
- interbreeding
- Migration
Carcinogens
X ray
- alters the DNA structure
Tobacco
- contains mutagenic agent (increase methylation of tumour suppressor genes)
1
, Sunday, 4 September y
- Results in a mutation
- mutation stops tumour suppressor gene
- results in uncontrolled cell division
Regulation of gene expression
Stem cells
A cell that can divide an unlimited number of cells
It is undifferentiated
It can differentiate into other cells
How do cells become specialised
- Transcription factors used to activate/deactivate genes
- mRNA transcribed Cells taken from an em-
bryo before first few cell from active genes
divisions
- mRNA used in transla- tion to make proteins
- Proteins give the cell a specific function Pluripotent
Embryonic vs induced pluripotent cells
Both Multipotent
- can differentiate into other cells Heart cells
- can divide indefinitely
- can prevent fatality
2
