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3.9 and 3.10 Genetic Variants and their Effects - Coggle Diagram
3.9 and 3.10 Genetic Variants and their Effects
Genetic Variants
Genetic variants are small changes in the order of bases that make up a strand of DNA
They can affect the structure of proteins in different ways, depending on whether they occur in coding DNA or non-coding DNA
Coding DNA
A genetic variant will alter the sequence of bases (e.g ACT -> AGT) and therefore will change the sequence of amino acids (e.g Glycine -> Valine)
This alters the final structure of the protein produced
Genotype and Phenotype
Genotype refers to the genes present in the DNA of an individual
Phenotype refers to the visible effects of those genes (e.g the proteins that they code for)
Non-Coding DNA
The enzyme RNA polymerase (see Section 3.8B) binds to non-coding DNA, and a change in the order of bases in this non-coding DNA can affect the amount of RNA polymerase that can bind to it
If less RNA polymerase is able to bind, less mRNA can be formed and the structure of the final protein is affected
A genetic variant in the coding DNA can affect phenotype differently
Mutations
Mutations change the sequences of bases in DNA
A base is deleted from the code
Like insertions they change the way it is read
It may change all the amino acids coded for after this deletion
A base is substituted
This will only change one amino acid in the sequence or it may not change the amino acid (as the new sequence can sometimes still code for the same amino acid)
A base is inserted into the code
It may change all the amino acids coded for after this insertion
As they are read in threes, this changes the way it is read
A change in the type/sequence of amino acids will affect the way it folds and therefore the structure
Most mutations do not alter the protein or only do so slightly
Most mutations do not alter the protein or only do so slightly
Some can have a serious effect and can change the shape
The substrate will not fit into the active site so it cannot act as a protein
A structural protein may lose its shape
There can also be mutations in the non-coding parts of DNA that control whether the genes are expressed