7.1: mutagens Flashcards
variation meaning
genetic differences between individuals
mutations
changes in genetic material of a cell; the altering of the sequence of nucleotides
- introduces new alleles into population
- can be spontaneous or due to environmental factors
mutagens
environmental agents that alter DNA and cause mutations
mutagenesis
the process of inducing a mutation, results in induced mutations
mutagenesis examples
- marie curie + radiation = leukemia
- rosalind franklin + x-rays = ovarian cancer
- bombing of hiroshima + ionising radiation = physical mutation
carcinogenic meaning
cancer-causing
- disrupts genes that regulate cell cycle + cell division
two types of gene mutations that lead to cancer
- proto-oncogenes
- tumor suppressor genes
chemical mutagens
chemicals which cause mutations if cells are exposed to them at high frequencies or for prolonged periods of time
- alters protein function, impairs cellular processes
examples of two types of chemical mutagens
- ingested chemicals: alcohol, tar in tobacco smoke, medications
- environmental irritants and poisons: organic solvents, asbestos, pesticides
structure of chemical mutagens
similar to purines + pyrimidines, incorporated accidentally into DNA during replication
- results in mispairing: insertion of incorrect nucleotides during replication, proteins don’t work
naturally occurring mutagens
mutagenic agents that are present at normal levels in natural environments, likelihood of mutation increased with increased frequency + length of exposure
two main groups of naturally occurring mutagens
- biological mutagens: viruses, bacteria, fungi, their products
- non-biological mutagens: metals, such as mercury and cadmium
biological mutagens + their actions
- end-products of metabolism, produced during metabolism by fungi, or plant and animal cells; e.g. when certain foods are eaten together, will form carcinogenic mutagens when cooked at high temperatures
- transposons: sections of DNA that spontaneously fragment/relocate/multiply
- microbes: may alter genetic materials in cells; able to insert own sequences, products may cause inflammation and reduced efficiency of DNA repair systems, some products may be unstable at cellular pH and break down and bind to DNA to alter it
physical mutagens
includes heat + ionising radiation
- heat: direct head combined with chemical/naturally occurring mutagens
- radiation: any transfer of energy through space from a source, ionising radiation has enough energy to break chemical bonds
EM waves
shorter wavelengths included in ionising radiation
- e.g. shorter UV, x-rays, gamma rays
UV
UVA(315-400): not ionising, prolonged exposure still bad
UVB(280-315) and UVC(180=280): ionising, causes chemical damage by breaking bonds, is mutagenic and carcinogenic
ionising radiation
high-energy radiation that is able to free electrons from atoms/molecules
- turns electrons into ions, which react with water when passing through cells to release free radicals
pyrimidine dimers
adjacent bases on the same strand attached
- most common effect of UV radiation rom sun on DNA
free radicals
highly reactive, may act on other parts of cell
- results in: break of DNA strand, partial chromosome loss, rearrangements of sequences in DNA, cross-linking of DNA itself
two main DNA repair mechanisms
- base excision repair: damaged/incorrectly paired base removed from sugar linkage + replaced
- mismatch repair: once DNA is replicated, polymerase carries out ‘spell check’ for accuracy
