6.1 mutations Flashcards
what is a mutation?
a mutation is a random change to the genetic material of an organism - some mutations involve changes to the structure or number of chromosomes
what is a gene mutation?
a gene mutation is a change to the DNA
when do mutations occur?
mutations may occur spontaneously during DNA replication before cell division
what are the two main classes of DNA mutation?
the two main classes of DNA mutation are:
- point/substitution mutation
- insertion or deletion (indel) mutation
what is a point mutation?
a point mutation is when one base pair is substituted for another
what is an insertion mutation?
an insertion mutation is when one more nucleotides are inserted into a length of DNA
what is a deletion mutation?
a deletion mutation is when one more nucleotides are deleted from a length of DNA
what do indel mutations cause?
indel mutations cause a frameshift
what are the three types of point mutation?
the three types of point mutation are:
- silent mutations
- missense mutations
- nonsense mutations
what is a silent mutation?
a silent mutation is where the base triplet still codes for the same amino acid
what is a missense mutation?
a missense mutation is when a change to the base triplet leads to a change in the amino acid sequence in a protein
what does a missense mutation have on the effect of the protein produced?
a missense mutation would lead to the alteration of the primary structure which leads to a change to the tertiary structure of the protein, altering its shape and preventing it from carrying out its usual function
what does a change in the tertiary structure prevent the protein from doing?
a change in the tertiary structure prevents the protein from carrying out its usual function
why does swapping one base with another have no effect on the protein produced?
swapping one base with another has no effect on the protein produced because each amino acid is coded for by more than one codon - this is referred to as the DNA code being degenerate
what does it mean that the DNA code is degenerate?
the DNA code is a degenerate code which means that the majority of amino acids are coded for by more than one codon
what is an example of a disorder caused by a missense mutation?
an example of a disorder caused by a missense mutation is sickle cell anaemia
what is a nonsense mutation?
a nonsense mutation may alter a base triplet, so that it becomes a termination triplet
what does a nonsense mutation result in?
a nonsense mutation result in a truncated protein that will not function
which genetic disease is a result of a nonsense mutation?
the genetic disease Duchenne muscular dystrophy is a result of a nonsense mutation
why will an indel mutation lead to a frameshift?
an indel mutation will lead to frameshift because the bases are read as triplets
what happens when a base pair is inserted or deleted from a DNA sequence?
when a base pair is inserted or deleted from a DNA sequence it has a knock-on effect on all subsequent base triplets
why is there a knock-on effect on all subsequent base triplets?
there is a knock-on effect on all subsequent base triplets because the code is non-overlapping
what happens when the mRNA from a mutated gene is translated?
when the mRNA from a mutated gene is translated, the amino acid sequence will be altered as well as the tertiary structure
what does inserting or deleting a whole base triplet result in?
inserting or deleting a whole base triplet results in the addition or loss of an amino acid
what does inserting or deleting a whole base triplet not result in?
inserting or deleting a whole base triplet does not result in a frameshift
what is Huntington disease a result of?
Huntington disease is a result of an expanding triple nucleotide repeat
what do some genes contain?
some genes contain a repeating triplet such as -CAG CAG CAG-
what is a repeating triplet known as?
a repeating triplet is known as an expanding triple nucleotide repeats
in an expanding triplet nucleotide repeat, at which stage does the number of triplets increase?
in an expanding triplet nucleotide repeat, the number of triplets increase at meiosis and again from generation to generation
what happens if the number of repeating CAG sequences goes above a certain critical number?
if the number of repeating CAG sequences goes above a certain critical number, then the person with that genotype will develop the symptoms of Huntington disease later in life
when are genetic mutations beneficial?
genetic mutations are beneficial to organisms during natural selection (antibiotic resistance for bacteria)
