mutations 1.4 Flashcards
mutation
a random change to an organisms genetic information (DNA)
what happens to proteins in a mutation
can result in no protein or an altered protein being synthesised or can have no effect on the phenotype
what increases the rate of mutations
mutagenic agents
examples of mutagenic agents
chemicals (mustard gas) and radiation (UV light)
genetic disorders
is a condition or disease related to an individuals genotype
what causes genetic disorders
caused by mutations which result in a protein not being expressed or a faulty protein being expressed
single gene mutation
involve the DNA nucleotide sequence being altered by one gene in a chromosome
point mutation
when only one nucleotide is changed
types of single gene mutations
substitution, insertion and deletion
substitution
occurs when one nucleotide is substituted (replaced) by another
what can substitution mutations cause
a missense or nonsense mutation or a splice site mutation
missense mutation
one amino acid is changed for another which may result in a non functional protein or it may have a little effect on the protein
nonsense mutation
altered mRNA codon is replaced by a stop codon so translation stops prematurely, the protein is shorted and doesn’t function
splice site mutation
-the removal of introns from the primary mRNA transcript during RNA splicing is controlled by splice sites that appear at the end of an intron before an exon
-when a mutation at one of these site causes an intron to be retained in error and/or an exon to be removed in error, the altered mRNA transcript may be translated into a protein that doesn’t function properly
what causes frameshift mutations
insertion or deletion mutations
what happens when a frameshift mutation occurs
all the codons and amino acids after the mutation are altered which has a major effect on the structure of the protein produced during translation
chromosome structure mutations
involves the change in the structure of one or more chromosomes and of the structure of a chromosomes changed it would bring about a change in the number or sequence of genes in that chromosome
types of chromosome structure mutations
inversion, deletion, duplication and translocation
inversion
occurs when a section of a chromosome is reversed (the genes switch places)
deletion (chromosome structure mutations)
occurs when a section of a chromosome is removed (genes are missing)
duplication
occurs when a section of one chromosome breaks off and joins onto its homologous partner (genes are duplicated in this chromosome)
translocation
occurs when a section of one chromosomes breaks off and joins onto another chromosome that is not its homologous partner
the two ways translocation can occur
non reciprocal translocation and reciprocal translocation
non reciprocal translocation
a section of deleted genes from chromosome 2 join onto chromosome 1
reciprocal translocation
a section of deleted genes from chromosome 2 join onto chromosome 1 and deleted genes from chromosome 1 join onto chromosome 2 (it’s been reciprocated)
lethal effect
chromosome structure mutations often involve substantial change to their structure and have a lethal effect on the individual affected
