Download Mutations

Mutations
Terms to study
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Mutation
Point mutation
Silent mutation
Missense mutation
Nonsense mutation
Nondisjunction
Protein synthesis
Semiconservative
replication
9. Transcription
10. Translation
11. Translocation
12. Duplication
13. Deletion
14. Inversion
15. Codon
Semiconservative Replication
The process in which the DNA molecule uncoils
and separates into two strands. Each original
strand becomes a template on which a new
strand is constructed, resulting in two DNA
molecules identical to the original DNA
molecule.
Mutations
• What are mutations?
• Mutations are changes in the DNA sequence
that affect genetic information. A permanent
transmissible change of genetic material
Types of Mutations – mistakes
1.Gene (point) Mutations – effects a single
gene
2. Chromosomal mutations – most drastic,
change in structure or # of chromosomes
(affects many genes)
Point Mutation
A single‐base substitution causing the
replacement of a single‐base nucleotide with
another nucleotide
Types of point mutations include : silent
mutation, missense mutation, and nonsense
mutation
Point Mutation
1. silent mutation- there is no change in an
amino acid
2. missense mutation- there is a different
amino acid
3. nonsense mutation- there is an insertion of a
stop codon in the amino acid which stops
protein synthesis
Frameshift Mutation
• Inserting or deleting one
or more nucleotides
• Changes the “reading
frame” like changing a
sentence
• Proteins built incorrectly
Gene Mutations
• Point Mutations – changes in one
or a few nucleotides
– Substitution
• THE FAT CAT ATE THE RAT
• THE FAT HAT ATE THE RAT
– Insertion
• THE FAT CAT ATE THE RAT
• THE FAT CAT XLW ATE THE RAT
– Deletion
• THE FAT CAT ATE THE RAT
• THE FAT ATE THE RAT
Example: Sickle Cell Anemia
Normal Red Blood Cell
• Red blood cells shaped like
a disc
• Hemoglobin (protien)
carries oxygen to all parts of
the body
Sickle Red Blood Cell
• Red blood cells form an
abnormal crescent shape
• Hemoglobin (protein) is
abnormally shaped
• don't move easily through
your blood vessels
• form clumps and get stuck
in the blood vessels
Chromosome Mutations
• Changes in number and structure of entire
chromosomes
• Original Chromosome
ABC * DEF
• Deletion
AC * DEF
• Duplication
ABBC * DEF
• Inversion
AED * CBF
• Translocation
ABC * JKL
GHI * DEF
Chromosomal Mutations
1. deletion, the loss of a segment of a
chromosome and thus the loss of segment
containing genes
2. duplication, when a segment of a
chromosome is duplicated and thus displayed
more than once on the chromosome
Chromosomal Mutation
3. inversion, when a segment of a chromosome
breaks off and reattaches in reverse order
4. translocation, when a segment of one
chromosome breaks off and attaches to a
nonhomologous chromosome
• Things that can cause mutations are called
“mutagens”.
• Known mutagens are ultraviolet light,
cigarette smoking, certain chemicals like
PCB’s, and other environmental factors.
Nondisjunction
• Failure of chromosomes to separate
during meiosis
• Causes gamete to have too many or too
few chromosomes
• Disorders:
– Down Syndrome – three 21st chromosomes
– Turner Syndrome – single X chromosome
– Klinefelter’s Syndrome – XXY chromosomes
Types of Gene Mutations
• Include:
–Point Mutations
–Substitutions
–Insertions
–Deletions
–Frameshift
Point Mutation
• Change of a single
nucleotide
• Includes the deletion,
insertion, or substitution
of ONE nucleotide in a
gene
Likelihood of chromosomal
mutations
1 in 1700 for mothers < 20.
1 in 1400 for mothers
>20<30.
1 in 750 for mothers
>30<35.
1 in 16 for mothers >45.