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12-4 and 5 Mutations and Gene
Regulation
I.
Kinds of Mutations in Genes
A. Point Mutations – mistakes
that occur at a single point in a
genes DNA sequence
1. Substitution - where one
Nitrogenous Base is
substituted for another
2. Insertion- where a Base is
included but does not
belong
3. Deletion- where a Base is
left out
B. Frameshift mutations - when
an insertion or deletion occurs
it causes a shift in the DNA’s
codons. Frameshifts can alter
proteins so much that they no
longer function.
C. Chromosomal Mutations- A
change in the number or
structure of chromosomes
1. Deletion- A section of a
chromosome is missing
2. Duplication- A section of a
chromosome is repeated
twice
3. Inversion- section of a
chromosome is flipped or
appears in reverse
4. Translocation- A section of a
chromosome gets misplaced
in another chromosome
D.Both types of mutations can
cause dramatic changes in
proteins and activities. Some
may cause problems others
may be beneficial. Mutations
cause diversity.
E. Polyploidy - A plant with an
extra set of chromosomes. In
plants this is often beneficial.
II.
Gene Regulation- How a Gene is
expressed in the cell
A. Operon- In Prokaryotes, a
gene has a repressor that
blocks the transcription
process
B. Promotor Sequence- In
Eukaryotes a promoter
sequence and TATA box
positions the RNA
polymerases for transcription
C. Regulation of Gene Expression
– A series of genes known as
hox genes control
development and
differentiation.
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