Transcript Chromosomal mutations

Mutations – change in DNA
Gene and Chromosomal
Mutations
Mutations
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2 Types:
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Gene mutations: Occur in DNA sequences (bases)
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Point (substitution)
Frameshift (deletion or insertion)
Chromosomal mutations: Occur in chromosomes
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Deletion
Duplication
Inversion
Translocation
Gene Mutations
Changes in bases of DNA
Types: Point and Frameshift
Point Mutation
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Substitution – Changes in one base
pair in DNA
Affects one AA
 Example: GCA vs. GTA
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Substitution
Frameshift Mutation
• Insertion – Addition of a base
• Deletion – Removal of a base
**Can affect all AA after it**
Example: TACGCA  TATCGC
Deletion
Insertion
Causes of Mutations
Spontaneous Mutations – Occur at random
Environmental Causes of Mutations X Rays, UV LIGHT, radioactive
substances, chemical exposure
Chromosomal Mutations
Changes in pieces of the chromosome
Types:
Deletion, Duplication, Inversion,
Translocation
Chromosome Structure
DNA wrapped
around
histone proteins
forming bead-like
units or
“nucleosomes”
These are coiled
forming a “super
coil” which coils to
form a
“chromosome”
Chromosomal Analysis
Karyotype – Photograph of
chromosomes of an individual
arranged by size and shape
Chromosome Determine Sex of Individual
Autosomes – Chromosomes that are the same in male and
female (chromosome pairs 1-22)
Sex chromosomes – One pair that determines sex (chromosome
pair 23- X is longer)
XX – Female, XY - Male
Normal Female
Normal Male
Problems with chromosome number result from defective
gametes.
They occur because homologous chromosomes separated
incorrectly during cell division (non-disjunction.)
This defective gamete becomes a part of the zygote and
new organism.
Chromosomes Number
Abnormalities
Trisomy – Diploid cell with an extra chromosome
Trisomy 13 (Patau Syndrome)
Trisomy 21 (Down’s Syndrome)
Down’s Syndrome – Trisomy 21
Patau’s Syndrome
Monosomy – Diploid cell missing a chromosome
(Turner’s Syndrome – Short Stature,
sterility, other health complications are possible)
Turner’s Syndrome
Polyploidy – An extra entire set of chromosomes;
plants with polyploidy tend to be heartier
Chromosome Structure
Abnormalities
Mutations- Change in genetic material
4 Types:
1. Deletion – Fragment breaks
off and is lost
2. Duplication –
Fragment breaks off and attaches
to homologous chromosomes
giving it two copies
3. Inversion –
Fragment breaks off and
reattaches backwards
4. Translocation–
Fragment breaks off and
joins non-homologous
chromosome
Many mutations don’t have an effect.
Some are harmful while others are helpful.
**They provide genetic variety in a species.
How can you tell the difference
between a gene mutation and a
chromosomal mutation?
Which is a gene mutation?
Which is a chromosomal mutation?