Answer
The five examples of mutagens
are X-rays, ultraviolet (UV) rays, bromouracil (BrU), nitrous acid, colchicine.
X-rays cause extensive
aberrations in chromosomes and genes, including breaks in DNA strand,
destruction or modifications of nucleotide bases or sugars. It may also results
in failure of organelles to function, prevent cell division or cause death of
cells, for examples, death of bone marrow cells.
UV radiation causes breakage of
A and T bases between the two complementary strands. Cross covalent bonding
then occurs between two adjacent thymine
bases on the same DNA strand to form thymine dimer. This will cause distortion
of the DNA helix, prevent normal base pairing and impede replication or
transcription.
Bromouracil resembles thymine
(has Br atom instead of methyl group). It can be incorporated into DNA and the
keto form of BrU can pair with adenine.
Nitrous acid causes deamination
of cytosine to produce uracil, and adenine to a guanine analogue would form
H-bonds with cytosine instead of base thymine.
Colchicine inhibits spindle
formation during cell division. The chromosomes do not separate to opposite
poles, causing the doubling of chromosomes.
Assignment submitted by L.Y., Kong, S. H., Lim, S. C., Soo, C. W.
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