Mutations • Mutations are changes of an individual’s
genetic information.
Can occur in
Somatic cells (Body cells)
◼Cannot be inherited
◼ can lead to cancer- like skin cancer
Gametes (Sex cells- egg and sperm)
◼Can be inherited
◼These are more notable, because they introduce genetic diversity and possible phenotypic changes in the population
• Spontaneous mutations in somatic cells cause tumors, diseases, and cancer, but are not passed on.
• Spontaneous mutations in germ cells affect the offspring and future generations.
Causes of mutation
1. Spontaneous (natural)– Spontaneous mutations can occur
during genetic processes • Such as DNA replication, recombination, or repair
• Proof-reading mechanisms prevent most mutation from happening in DNA Replication, but they aren’t so good during protein synthesis
2. Induced (caused by mutagens)
– Physical Mutagens:
• Some forms of electromagnetic radiation (X-rays and Ultra Violetlight)
– Chemical Mutagens:
• Pesticides
• Tobacco smoke
• Environmental pollutants
6
Types of mutations
– Gene Mutations • Changes in a single base pair of a gene, also called point mutations
-Chromosomal Mutations
• Involves a change in the structure
• Or the number of chromosomes
Gene Mutations: Substitution
Gene Mutations 1) Point Mutations: occur at a single point. Change
in ONE letter (base) in the DNA.
All point mutations are a results of SUBSTITUTION( one nucleotide replaces another)!!!!
-Silent mutations: have no effect on the amino acid produced.
-Missense mutations: still code for an amino acid, but not the correct amino acid.
- Nonsense mutations: change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein
Gene Mutations 2) Frameshift Mutations
Gene Mutations 2) Frameshift Mutations: are mutations caused by insertion or deletion of the bases, which results in a shift of the “ reading frame” of the genetic message.
This type of mutation can change every amino acid that follow the point of the mutation and can alter a protein. Most dangerous type of mutation
Insertions and Deletions• Insertions: addition of nucleotide pairs in a gene
• Deletions: losses of nucleotide pairs in a gene
• Insertion or deletion of nucleotides may alter the reading frame, producing a frameshift mutation
© 2011 Pearson Education, Inc.
Chromosomal Mutations • Changes to the number of chromosomes
• Changes to the structure of the chromosome
• Four types exist:
A B C D E F G HDeletion
A B C E G HF
A B C D E F G HDuplication
A B C B D EC F G H
A
A
M N O P Q R
B C D E F G H
B C D E F G HInversion
translocation
A B P Q R
M N O C D E F G H
A D C B E F HG
• Deletion: removes a chromosomal segment.
• Duplication: repeats a segment.
• Inversion:reverses a segment within a chromosome.
• Translocation: moves a segment from one chromosome to another, nonhomologous one.
The “good”, the “bad”, and the “indifferent”
• Based on their effects on fitness, mutations can be divided into three broad categories:
1. the ‘good’ or advantageous that increase fitness,
2. the ‘bad’ or deleterious that decrease it
3. and the ‘indifferent’ or neutral that are not affected by selection because their effects are too small.
Example: Point Substitution Mutation
Pedigree of Sickle-Cell Mutation
hh HH
HH
Hh HhHhHhHh
HhHhhh
What is a mutation?
A. the specific sequence of bases in a molecule of DNA
B. the perfect replication of a DNA molecule
C. the process by which a molecule of DNA makes a copy of itself.
D. a change in the genetic material.
Which type of mutation occurs when one base in DNA is replaced
by another?A. frameshift mutation
B. point mutation
C. chromosomal mutation
D. nondisjunction
1.
2.
3.
4.
Which type of mutations is shown?
A. insertion
B. substitution
C. duplication
D. translocation
A. insertion
B. substitution
C. duplication
D. translocation
Which type of mutations is shown?
What is the cause of the mutation shown in the
karyotype below?A. inversion
B. frameshift
C. nondisjuntion
D. translocation
Consider the following statements:
• I. Mutations always have a negative effect on an individual.
• II. Mutations can have a positive effect on an individual.• III. Mutations can have no effect on an individual.• IV. Mutations can have a negative effect on an individual.
Which statement above is/are true?
A. I onlyB. I and II onlyC. II, III, and IV onlyD. I, II, III, IV