Page 23 - CB1.3 Genetic Varation sciPAD

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CB 1.3 GENETIC VARATION
PRINCIPLES OF GENETIC VARIATION
Mutant mice get fat on poison
Mice have found ways of outwitting
humans in the matter of survival - by
evolving resistance to a common poison.
New research by Michael Kohn and
colleagues at Rice University suggests a
genetic mutation has given the ordinary
house mouse this extraordinary ability.
Warfarin is a chemical used to kill rodents. It works
by thinning their blood and preventing it from
clotting. Given in sufficient amounts, warfarin
will cause animals to bleed to death internally.
When warfarin is used it has been found that some
mice were resistant to its effects. The more warfarin
was used the more common resistant mice became.
Kohn, associate professor of ecology and
evolutionary biology at Rice, said the mice evolved
to become poison resistant due to a previously silent
mutation. Because the reproductive generation
time in mice is so quick, this mutation was able
to spread quickly. “A key element of this study is
that we’ve caught evolution in the act,” he said.
The use of warfarin as a rodent poison is now
declining because many mouse populations
have developed complete resistance to it.
5. Complete the following paragraph using the word list.
body - allele - gametes - inherited - variation
Mutations can change an or create a new one. This may cause
an increase in the within a population. Mutations that occur in
cells (somatic cells) are not passed on to the offspring (i.e. they
are not ). Only mutations that occur in
(sex cells) can be passed on to the offspring.
6. Read the article below and answer the questions that follow.
(a) Outline why some mice are resistant to warfarin. 



(b) Describe how changes in the DNA of the mice led to some of them being resistant.



(c) State whether this change in the mice DNA occurred in the somatic (body) cells or
in the gametic (sex) cells. Justify your answer. 



7. Albinism is a mutation that causes an organism to be born without any pigmentation in
its skin. Albinism affects a number of animals, including humans. Albino rabbits are very
common in captivity but are almost never seen in the wild.
Give reasons why albino animals are very rarely found in natural environments, but are quite
common in captivity. 



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