Download Genetic Mutation

21.7 Genetic Mutations
A peacock with
albinism does not
produce the melanin
needed to make
bright colors for its
feathers.
Learning Goal Identify the type of change in DNA for a point
mutation, a deletion mutation, and an insertion mutation.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Genetic Mutation
A mutation
• is a change in the nucleotide sequence of DNA.
• may result in changes to the sequence amino acids
that affect the structure and function of cells.
• results from mutagens, such as radiation and
chemicals (possibly some viruses).
When a mutation severely alters proteins or enzymes, the
new cells may not survive or the person may exhibit a
disease or condition that is a result of a genetic defect.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Normal DNA Sequence
The normal DNA sequence produces an mRNA
that provides instructions for the correct series of
amino acids in a protein.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Types of Mutations
• A point mutation is the replacement of one base in the template
strand of DNA with another; this may cause a different amino acid to
be inserted into the polypeptide.
• A silent mutation occurs when a point mutation does not change
the amino acid.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Mutations, Deletion and Insertion
• In a deletion mutation, a base is deleted from
the normal order of bases in the template strand
of DNA. All the codons that follow are changed,
producing a different sequence of amino acids
from that point.
• In an insertion mutation, a base is inserted into
the normal order of bases in the template strand
of DNA. All the codons that follow are changed,
producing a different sequence of amino acids
from that point.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Mutations, Deletion and Insertion
Deletion and insertion mutations change all the
codons that follow.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Effects of Mutations
• Some mutations do not cause significant changes in the primary
structure of a protein.
For drastic changes in the amino acid sequence,
• the structure of the resulting protein may lose its biological
activity.
• proteins (enzymes) may no longer catalyze reactions and
substances may accumulate in the cells until they are poisonous.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Genetic Diseases
• Genetic diseases result from a defective enzyme caused by mutation in
its genetic code.
• If the enzyme that converts tyrosine to melanin is defective, no melanin
is produced, resulting in the genetic disease known as albinism.
• Tyrosine is needed for the formation of melanin (skin and hair pigment).
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Genetic Diseases
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Identify each type of mutation as a point mutation (P), an insertion
mutation (I), or a deletion mutation (D).
A. Cytosine (C) enters the DNA sequence.
B. One adenosine is removed from the DNA sequence.
C. A base sequence of TGA in DNA changes to TAA.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Identify each type of mutation as a point mutation (P), an insertion
mutation (I), or a deletion mutation (D).
A. Cytosine (C) enters the DNA sequence.
(I)
B. One adenosine is removed from the DNA sequence. (D)
C. A base sequence of TGA in DNA changes to TAA.
(P)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.