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MUTAGENS (CHEMICAL MUTAGENS (chemicals that cause mutations (large number…
MUTAGENS
CHEMICAL MUTAGENS
chemicals that cause mutations
if cells exposed at high frequencies or for long time
large number of ingested & everyday chemicals
mutagenic over time
no longer widely used
cause DNA change
alters function of proteins & impairs cellular processes
EXAMPLES
ingested chemicals
alcohol
tar (tobacco smoke)
some medications
chemicals in food
charred/fatty foods
food additives & preservatives (e.g. nitrites)
environmental irritants & poisons
organic solvents (e.g. benzene)
cleaning products
asbestos
coal tars
pesticides
some hair dyes
mutagenic chemicals = structurally similar to normal DNA bases
mistakenly incorporated into DNA during replication
= insertion of incorrect nucleotides opposite during replication ["mispairing"]
insertion = non-functional protein end product
EXAMPLES
alkylating agents
de-aminating agents
intercalating agents
PHYSICAL MUTAGENS
include heat
direct heat = combined action w/ chemical & naturally occurring mutagens
include ionising radiation
enough energy to break chemical bonds in molecules, including DNA
electromagnetic radiation
from sun
energy all around (e.g. radio waves, microwaves, gamma rays)
ultraviolet (UV) radiation
UVA is non-ionising
UVB & UVC are ionising
naturally occurring UV radiation from sun
contributes to skin cancer
produces pyrimidine dimers
adjacent pair of bases on same strand attach to each other --> prevents pairing w/ complementary bases = strand ends prematurely
prevents normal replication & transcription = affects cell cycle & gene products
many mutagens are carcinogenic
mutations occur genes that regulate cell cycle or promote/suppress cell division
cause changes in cell cycle = increased cell division w/o differentiation
= cell masses 'tumours'
2 types genes
proto-oncogenes
tumour suppressor genes
NATURALLY OCCURRING MUTAGENS
some mutations arise from exposure to naturally occurring mutagens in the environment
spontaneous mutations: arise in DNA replication & are retained b/c normal mechanisms of DNA repair doesn't correct
mutagenic agents present at normal natural environment levels --> may cause mutations
mutation likelihood increases w/ increased frequency + exposure length
2 groups
biological mutagens
include viruses, bacteria, fungi & their products
ACTIONS
end-products of metabolism
mutagens produced by fungi, or plant/animal cells in metabolism
mutagens found b/c sudden outbreak of cancers
e.g. nitrosamine
transposons
DNA sections spontaneously fragment & relocate/multiply within genome
transposable elements insert into chromosomal DNA
disrupt DNA functioning
microbes
viruses (e.g. hepatitis B virus, HIV, Epstein-Barr virus, Rubella virus)
bacteria (e.g. Helicobacter)
may directly alter cell's genetic material
EFFECTS
microbes insert own base sequences into DNA --> changes gene functioning & triggers cancers
inflammation --> free radicals produced cause DNA damage & reduce DNA repair system efficiency
non-biological mutagens
include natural metals (e.g. mercury & cadmium)
MUTAGENS: environmental agents that alter DNA & cause mutations
MUTAGENESIS: process of inducing a mutation
INDUCED MUTATIONS: resulting mutations