Transcript Mutation Notes - West Branch Schools

Mutations
Mutations
• A permanent change in a cell’s DNA
• Rare
• Some cells have repair mechanisms to fix
some damage
Types of Mutations and Resulting
Phenotypic Changes
• Translocations - Translocations are the transfer of a piece
of one chromosome to a non-homologous chromosome.
They are often reciprocal, with the two chromosomes
swapping segments with each other.
• Example: Cancer: several forms of cancer are
caused by acquired translocations (as opposed to
those present from conception); this has been
described mainly in leukemia
Types of Mutations and Resulting
Phenotypic Changes
• Inversion - A region of DNA on the chromosome can flip
its orientation with respect to the rest of the chromosome.
• Example: Opitz-Kaveggia syndrome (FG Syndrome) X-linked
causes mental retardation, short stature, low muscle tone, and
respiratory condition…usually males
Types of Mutations and Resulting
Phenotypic Changes
Deletions - A large section of a chromosome
can be deleted resulting in the loss of a
number of genes.
•Ex:Cystic fibrosis-characterized by abnormally
thick mucus in the lungs, intestines, and pancreas
Types of Mutations and Resulting
Phenotypic Changes
 Duplications - In this mutation, some genes are
duplicated and displayed twice on the same
chromosome.
 Example: Charcot-Marie-Tooth Disease-damage to
peripheral nerves leading to weakness and atrophy of
muscles in hands and lower legs
Types of Mutations and Resulting
Phenotypic Changes
 Insertion-addition of one or more nucleotide base pairs into a
DNA sequence
 Example: Crohn’s disease: chronic inflammation of the
intestinal tract, leading to diarrhea, nausea, etc.
Types of Mutations
 Nondisjunction-Failure of chromosomes to separate
 Example: Down Syndrome
Causes of Mutations
• Spontaneously
• Chemicals- change the chemical structure of the bases (mispairing or
bond with wrong base)
• Some chemicals are so similar to the base they can mimic the properties
and act as a substitute
• Radiation- X-rays and gamma rays
• UV radiation causes adjacent thymine bases to bind together disrupting
the DNA sequence and prevents replication
– Mutation Video
Explain the relationship between…
• Mutation,
• Cell cycle
• Uncontrolled cell growth
• Cancer
Cancer is….
 An abnormal mass of cells with uncontrolled cell growth.
 2 Types
 Benign- a mass of normal cells growing out of control
 Malignant- mass of abnormal cells growing out of control
• Proto-oncogenes-normal gene that can become an oncogene due
to mutations or increased expression. Proto-oncogenes code for
proteins that help to regulate cell growth and differentiation.
• Oncogenes (cancer causing gene)- is a gene that, when mutated or
expressed at high levels, helps turn a normal cell into a tumor cell.
Many abnormal cells normally undergo a programmed form of
death (apoptosis). Activated oncogenes can cause those cells to
survive and proliferate instead
• Tumor-Suppressor Genes- code for proteins that serve as the
"stop" signals prohibiting cell cycle from dividing
• Cancer Video
How do Phenotypic Changes Occur
• If a mutation occurs in a germ-line cell (one that will give
rise to gametes, i.e., egg or sperm cells), then this mutation
can be passed to an organism's offspring
• As opposed to germ-line mutations, somatic mutations occur
in cells found elsewhere in an organism's body. Such
mutations are passed to daughter cells during the process of
mitosis, but they are not passed to offspring conceived via
sexual reproduction.