Genetic Mutations and Meiosis Flashcards
What is a genetic mutation?
A change in a sequence of base pairs in a DNA molecule?
What effects can a genetic mutation have?
They could alter the codon which would change the amino acid coded for. This may even alter the polypeptide produced.
Or, there may be no effect as several codons code for the same amino acid, meaning there is no change. This because code is degenerate.
What is an insertion?
What effect could it have?
A nucleotide is inserted into the base sequence. This creates a frame shift downstream in the sequence.
What are deletions?
What effect could they have.
A nucleotide is removed from the base sequence.
This causes a frame shift down stream, so all nucleotides shift backwards.
How would a deletion/insertion at the start of a DNA sequence compare to one at the end?
If the mutation occurred at the start then the frame shift would be bigger, causing a bigger effect on the polypeptide coded for.
What are substitutions?
Why are they usually less bad than insertions/deletions?
A nucleotide is swapped for a different nucleotide.
They do not cause a frame shift, so if the amino acid is altered then it will only be one that has changed.
What is a silent mutation?
Where the mutation has no effect on amino acid production, so the polypeptide coded for stays the same.
What are missense mutations?
Where only one amino acid in a DNA sequence is changed.
What are nonsense mutations?
Where the mutation results in production of a stop codon, so production of a polypeptide is terminated early.
Explain the overall effect mutations may have on polypeptide production.
Mutations typically have little effect on polypeptide production. This is because code is degenerate, so many codons may code for a single amino acid.
How do gene mutations typically arise?
Spontaneously, or are caused by a mutagenic agent
What are mutagenic agents?
Environmental factors that speed up the rate of mutation in a gene.
Give an example of a mutagenic agent.
Ionising radiation such as xrays.
Name 2 ways that chromosome mutations arise.
Spontaneously
Through fertilisation of abnormal gametes.
How do non disjunction mutations arise and what can they do to gametes?
Where individual homologous pairs of chromosomes fail to separate during meiosis, leading to gametes having extra or no copies of a chromosome.
