Genes and Proteins in Health and Disease (Single Gene Mutations (Point…
Genes and Proteins in Health and Disease
Proteins are complex chain molecules made up of amino acid groups joined by peptide bonds. The amino acids are sequenced for the protein to fit a specific function and the Protein can also be shaped by folding, by bonding to itself with hydrogen bonds and sulphur bridges.
Mutations are random changes in he genes which can cause changes in the expressed protein.These range from simple single nucleotide mutations to chromosome mutations. If the change in the genotype leads to a change in phenotype the organism can be refereed to as a mutant organism.
The chances of a mutation occurring can be increased with exposure to mutagenic agents, such as mustard gas and ionising radiation. Mutations are also important to the evolution of species as it creates variation within the genome.
Single Gene Mutations
Point mutations are changes within a single nucleotide, and therefore base, in the DNA sequence.
There are 3 types of Point mutation
Where one nucleotide is added to the DNA strand, this causes a major change in the Protein produced this causes frameshift where the whole gene is displaced
Where one nucleotide is removed, this causes a major change in protein structure this causes frameshift where the whole gene is displaced
Where one nucleotide is replaced by another, this causes a minor change in the Proteins structure
Substitution Mutation Types
CHANGE: One codon to a STOP codon
This causes a shortened protein to be formed and so possibly wont be able to fit its function or will fit another function
CHANGE: A substitution happening between introns and exons
This causes a possible prevention of splicing and a very different protein being produced as introns may be left in the transcript
CHANGE: One codon to another
This causes a possible change in protein shape and a different amino acid being produced but also may not have
Single Nucleotide Repeat Expansion
A large expansion of a codon which is inserted many times which can go on for hundreds of repeats producing a defective protein
Chromosome Mutations are alterations to an entire chromosome and therefore large parts of the organisms genome.
There are 3 types of Chromosome mutations
results from the breakage of a chromosome and causes genetic material to be lost in cell division
Where a gene section from one chromosome breaks and reattaches to another chromosome, this can happen with multiple chromosomes at once ending in reciprocal translocation
Where extra copies of a gene are produced on the end of a chromosome