19.1 mutations and variation Flashcards
what is a mutation?
change in the sequence of bases in DNA
how is protein synthesis affected by a mutation?
the wrong bases and transcribed which means that translation would lead to the wrong amino acids being produced and thus a different primary structure of a protein
so the final 3D structure may change
what are the three types of mutation?
substitution
deletion
insertion
what is a substitution mutation?
when a nucleotide is substituted for another which leads to a different codon
when can a substitution mutation lead to no change?
when the codon replacing the original codon codes for the same amino acid and so the same protein is produced
DEGENERATE NATURE OF GC
what is a deletion mutation?
when one or more nucleotides are removed
what is an insertion mutation?
when one or more nucleotides are added
what does insertion and deletion lead to?
a frameshift mutation
what is a frameshift mutation?
by adding or removing a nucleotide, you displace the following codons which, due to the non-overlapping nature of the GC, changes every successive codon
so changes the base sequence
what are the 3 effects of a mutation?
no effect
damaging
beneficial
no effect
mutation causes no effect on the phenotype of an organism
damaging
mutation causes major change to an organism’s phenotype which prevents essential processes
beneficial
mutation causes a change to an organism’s phenotype which provides an advantageous characteristic
when can a mutation have no effect?
mutation changes a base in a codon but the codon stays the same so the same amino acid is translated
mutation changes a base in a codon and a different amino acid is translated BUT the new amino acid is chemically similar to the original so functions very similarly
how do mutations occur?
spontaneously during DNA replication
what is a mutagen?
an agent which causes mutations
increases the rate of mutations
what is depurination?
the loss of a purine base
what is depyrimidination?
the loss of a pyramidine bae
what do depurination and depyrimidination cause?
leads to the incorrect base being used through complimentary base pairings
what are the effects of free radicals on nucleotide structure?
they disrupt base pairing in DNA replication
what is a silent mutation?
mutation which has no effect on the phenotype
what is a nonsense mutation?
mutation which causes a stop codon to be synthesised which shortens the protein structure
what is a missense mutation?
mutation which causes the wrong amino acid to be synthesised
how is lactose-tolerance a beneficial mutation?
allows a mammal to digest lactose
what are the mutations a chromosome can undergo?
deletion
duplication
translocation
inversion
deletion in a chromosome
section of a chromosome breaks off and is lost in the cell
duplication in a chromosome
sections of a chromosome get duplicated
translocation in a chromosome
section of a chromosome breaks off an joins a non-homologous chromosome
inversion in a chromosome
section of a chromosome is removed, reversed and then reinstated
