DNA - MUtations

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DNA - MUtations
GENE Mutations
CHROMOSOMAL Mutations
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DNA - Mutations
A third key function/ability of DNA is that it
can undergo a mutation. Most of the time these
mutations are negative, but on occasion a newer
better form of a gene may be produced.
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• The two major categories of Mutations are
• Gene Mutations
• Chromosomal Mutations

Chromosomal mutations affect a chunk of a
chromosome and therefore may affect dozens of
genes.
Gene mutations affect one gene.
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Lets start by looking at Chromosomal Mutations.
Most Chromosomal mutations occur when Homologous
chromosomes line up with each other and a piece
of one chromosome breaks off and switches places
with the complimentary piece on its partner
chromosome.
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This process is called Crossover and its purpose
is to create more variation in the chromosomes
that can be passed onto offspring in the sex
cells Eggs and Sperm
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Crossover
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DELETION
Sometimes during crossover, a piece of chromosome
breaks off and moves over to the other
chromosome, but the piece that is supposed to
come in and replace it does not do so.
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Example Williams Syndrome
Chromosome 7
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DUPLICATION
Sometimes during crossover, a piece of chromosome
from the homologous (partner) chromosome comes in
and joins on, but the piece that it was supposed
to replace, never left.
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Example Inv Dup 15 Syndrome
Seizures, scoliosis and mental retardation
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INVERSION
Sometimes during crossover, the proper piece will
come in but it will insert itself backwards
(inverted) into the existing chromosome.
Even though all the genes (d,e, and f) are
replaced, they cannot be properly read, because
they are being read backwards.
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TRANSLOCATION
In the final type of chromosomal mutation, two
chromosomes line up and undergo crossover, but
they are not homologous. So for example instead
of chromosome 5 matching up with another 5, it
lines up and exchanges sections with chromosome
18. That is really bad!
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Affects the liver, heart kidney, and other
systems of the body. Problems associated with the
disorder generally become evident in infancy or
early childhood.
Example Alagille Syndrome
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summary