19.1 Mutations and variation Flashcards
(14 cards)
What’s a mutation
change in the sequence of bases in DNA which may affect the phenotype
What’s point mutation
When only one nucleotide is affected
What are the effects of mutations
No effect - there’s no effect on the phenotype as normally functioning proteins are still synthesised
Damaging - there’s phenotype is affected in a negative way as proteins are no longer synthesised or are non functional this can interfere with more essential processes
Beneficial - very rarely a protein is synthesised that results in a new and useful characteristic in the phenotype
What causes mutations
Mutations can occur spontaneously often during DNA replication but the rate of mutation is increased by mutagens (a chemical physical or biological agent which causes mutations)
What are some of the main mutagens
Physical _ ionizing radiations eg. X-rays (breaks DNA strands)
Chemical - deaminating agents (alters bases in dna eg a—> c)
Biological - alkylating agents, base analogs & viruses (attached methyl or ethyl groups to bases= incorrect base pairing)
(Added into dna instead of the usual base)
(Viral DNA can insert itself into a genome)
What’s substitution
When one base is substituted for another eg. A —> C this changes the code in which it occurs so if the new code changes the amino acid which it codes for the the whole primary structure and therefore protein changes
However the new codon may a still code for the same amino acid as the last one
The position and involvement of the aa in R group interactions will determine the impact of the new aa on the function of the protein
What’s insertion and deletion
The insertion (right) or deletion (left) is adding or removing a base which leads to frameshift mutation as every codon is changed from the point of mutation
What’s an example of beneficial mutation
The ability to digest lactose is a result of a mutation
What can changes in the chromosome structure by mutation include;
Deletion
Duplication
Translocation
Inversion
What’s deletion
A section of chromosome breaks off and is lost within the cell
What’s duplication
Sections get duplicated on a chromosome
Whats Translocation
A section of one chromosome breaks off and joins another non homologous chromosome
Whats inversion
A section of chromosome breaks off is reversed and the joins back onto the chromosome
What’s chromosome mutation
A mutation that affects the whole chromosome or many chromosomes within a cell the can be caused by mutagens or in meiosis and can be silent but often lead to development difficulties
