CHROMOSOME STRUCTURE MUTATIONS
1.3 Genome: (b) ii Chromosome structure mutations
From the Arrangements
(ii) Chromosome structure mutations
Alterations to the structure of one or more chromosomes: duplication,
deletion, translocation and inversion. Importance of gene duplication in
evolution.
Teacher’s notes
As an introduction the following link provides a slideshow that illustrates
chromosomal structure mutations:
http://ghr.nlm.nih.gov/handbook/illustrations/chromosomechanges?show=bal
ancedtranslocation
The vast majority of the slides are pitched at just the right level, although
there are one or two that show that there are other types of mutations. To
avoid confusion you may wish to stop the slideshow at inversion.
The following work card is straightforward and relatively easy.
The learning points and instructions have been preceded with a smiley face
(☺) and underlined.
The last ☺ is almost an open-ended question relying on the students’
previous knowledge of the genome. For example, they may think the
duplicated genes or chromosomal section may be inserted on a chromosome
therefore interrupting and mutating an existing gene. It is also the case that
some cancers are associated with duplicated genes (called oncogenes).
Duplication of genes has been important in plant and fish evolution,
particularly in plants.
As an aside:
This 3.5 minute video clip (Ken Miller Human Chromosome 2 Genome) gives
an interesting and easy-to-follow account of chromosomal translocation in
terms of human evolution:
http://www.youtube.com/watch?v=8FGYzZOZxMw
(You can download these clips into mp4 format using the Zamzar website.)
UNIT 1, PART (III) GENOME (H, BIOLOGY)
© Learning and Teaching Scotland 2011
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CHROMOSOME STRUCTURE MUTATIONS
There are also questions related to this type of mutation in the old version of
Higher Biology.
The last question should be straightforward. Emphasise to students that by
altering sections of chromosomes, individual genes may be affected
depending on where chromosomes break or insertions occur.
Student activities
Chromosome structure mutations
Definitions
Loss of a piece of DNA from a
chromosome (loss of a gene or part of
a gene) can lead to a disease or
abnormality.
Breakage and removal of a large
segment of DNA from one
chromosome, followed by the
segment’s attachment to a different
chromosome.
Production of one or more copies of
any piece of DNA, including a gene or
even an entire chromosome.
A type of chromosomal abnormality in
which a DNA sequence is inserted into
a gene, disrupting the normal structure
and function of that gene.
Where a section of the chromosome is
turned upside down.
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UNIT 1, PART (III) GENOME (H, BIOLOGY)
© Learning and Teaching Scotland 2011
CHROMOSOME STRUCTURE MUTATIONS
☺ You will need to know the different types of chromosome structure
mutations and how duplication of chromosomes is important in
evolution.
After studying the above information draw representations of deletion,
duplication, inversion, insertion and translocation then copy out the
correct definition next to your drawing.
☺ Copy the following.
Duplication is thought to be one of the driving forces of evolution: if an
organism has two copies of the same gene and one become s mutated the
other will still function normally, preventing any negative consequences.
The lack of any deleterious effects may allow the development (mutation)
of new genes, which could give the organism an advantage over its
competitors. If the organism is better adapted to its environment then it
will stand a greater chance of surviving and passing its genes onto the next
generation.
☺ Explain why you think not all chromosomal duplication mutations may
be beneficial?
UNIT 1, PART (III) GENOME (H, BIOLOGY)
© Learning and Teaching Scotland 2011
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