Mutations
Although changes in an organism’s hereditary information are rel-
atively rare, they can occur. As you learned in Chapter 6, a change
in the DNA of a gene is called a mutation. Mutations in gametes
can be passed on to offspring of the affected individual, but muta-
tions in body cells affect only the individual in which they occur.
Mutations that move an entire gene to a new location are called
gene rearrangements. Changes in a gene’s position often disrupt the
gene’s function because the gene is exposed to new regulatory con-
trols in its new location—like what would happen if you moved to
France and couldn’t speak French. Two types of gene rearrange-
ments are shown in Figure 8.Genes sometimes move as part of a
transposon. That is, the genes are carried by the moving transposon
like fleas on a dog. Other times, the portion of the chromosome
containing a gene may be rearranged during meiosis.
Mutations that change a gene are called gene alterations. Gene
alterations such as those shown in Figure 8 usually result in the
placement of the wrong amino acid during protein assembly. This
error can disrupt the protein’s function. In a ,a sin-
gle nucleotide changes. In an insertionmutation, a sizable length
of DNA is inserted into a gene. Insertions often result when
mobile segments of DNA, called transposons, move randomly
from one position to another on chromosomes. Transposons
make up 45 percent of the human genome. In a deletionmutation,
segments of a gene are lost, often during meiosis.
point mutationSECTION 2Gene Regulation and Structure 219
No Mutation
ABCACAB CAB B CGene Alterations
Point mutationInsertionDeletionGene Rearrangements
TranspositionACBBChromosomal rearrangement
ABBCThe substitution, addition, or removal of one or more
nucleotides is called a gene alteration. If the mutation
changes the original position of a gene of the chromo-
some, the gene may not function normally.
Figure 8 Major types of mutations
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Topic: Genetic Disorders
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Keyword: HXX4008