Mutation Flashcards
What is a gene?
A sequence of bases in DNA that code for a sequence of amino acids in a polypeptide.
What is a mutation?
A mutation is any change to the quantity or the base sequence of the DNA in an organism.
What is a gene mutation?
Any change to 1 or more nucleotide bases, or a change in the sequence of the bases in DNA.
What are the 2 types of gene mutation?
Substitution and deletion
What is substitution?
When a base is swapped/replaced by a different base.
How does substitution affect the amino acid?
The effect of substitution on the amino acid will depend on the precise role of it.
A mutation can change the structure of the protein, effecting its ability to function.
Or
A mutation can have no effect on the protein. this can occur when the new triplet of bases codes for the same amino acid.
What is deletion?
When a base is missed out/deleted.
A gene mutation by deletion occurs when a nucleotide is lost from the normal DNA sequence.
What affect does deletion have on the polypeptide?
It changes the sequence of the polypeptide chain so that its entirely different. Therefore, the polypeptide is unlikely to function properly.
Missing out a base causes all triplets in the sequence to be read differently because each has been shifted to the left.
When do mutations occur?
Spontaneously during cell replication.
Mutagenic agents increase the rate of mutations e.g radiation and chemicals that alter the DNA structure or interfere with transcription.
What are chromosome mutations?
Changes in the structure or number of whole chromosomes.
Chromosome mutations occur spontaneously and take 2 forms …
Changes in whole sets of chromosomes.
Changes in the number of individual chromosomes.
When do changes in whole sets of chromosomes occur?
Occurs when organisms have 3 or more sets of chromosomes rather than the usual 2. This condition is called polyploidy and occurs mostly in plants.
When do changes in the number of individual chromosomes occur?
Sometimes individual homologous pairs of chromosomes fail to separate during meiosis. This is known as as non-disjunction and usually results results in a gamete having either 1 more or 1 fewer chromosome.
What are the 3 effects of mutation?
Production of a new/superior protein - gains a reproductive advantage.
Neutral mutation - No change
Production of inferior or no protein - Fatal and/or disease causing.
