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Mutations, Sex-linked traits, Disorders, Pedigrees
What’s a Mutation?
A change in DNA sequence Two types:
Changes in a single gene(called gene mutation)
Changes in a whole chromosome(called chromosomal mutation)
What’s a Mutation?
Gene Mutations: Two types… 1. Point Mutation
One nucleotide is affected …that is…
ONE LETTER IS WRONG!
TTA-GTA-CCG becomes
TAA-GTA-CCG (usually changes one amino acid in a
protein)
What’s a Mutation?
Gene Mutations: Two types… 2. Frameshift Mutation
Addition or deletion of one letter (nucleotide) Sequence is “read” one letter off from correct
way
TTA-GTA-CCG becomes
TTT-AGT-ACC-Gthesunwashotbuttheoldmandidnotgethishat
What’s a Mutation?
Chromosomal Mutations 1. Deletion
Part of chromosome is missing
What’s a Mutation?
Chromosomal Mutations 1. Deletion
Part of chromosome is missing 2. Duplication
Part of chrom. is included twice
What’s a Mutation?
Chromosomal Mutations 1. Deletion
Part of chromosome is missing 2. Duplication
Part of chrom. is included twice 3. Inversion
Part of chrom. is reversed from usual direction
What’s a Mutation?
Chromosomal Mutations 1. Deletion
Part of chromosome is missing 2. Duplication
Part of chrom. is included twice 3. Inversion
Part of chrom. is reversed from usual direction
4. Translocation Two non-homologous chrom. exchange
portions
Mutagens
Can alter DNA’s ability to be edited (corrected)
Affects gamete and somatic cell formation
Sources Ultraviolet radiation Radioactive substances X - rays Chemical exposure
What’s a Mutation?
Some mutations are significant and severe, some are less so, some are never noticed…
Consider the car…
Sex-Linked Traits
Sex-linked diseases are X linked… The sex chrom. are the X and y
Consider Hemophilia (the inability for blood to clot properly)
Also Colorblindness (the inability to distinguish certain
colors)
Gene that can cause it found on X chrom.
Sex-Linked Traits
Hemophilia (sex-linked recessive) Females/Males:
XH XH Female, clots XH Xh Female, clots
(carrier) Xh Xh Female, can’t clot
XHy Male, clots Xhy Male, can’t clot
Other Disorders
While mutations are generally gene related and inherited from one or both parents, sometimes OTHER reasons cause problems…
NONDISJUNCTION The parent’s genes can be fine. But
during MEIOSIS of the gametes, too many or too few chromosomes were pulled into the new gamete cell…
Normal Male Karyotype:22 sets of autosomes, 1 set of sex chromosomes
Inheritance Patterns
AUTOSOMAL DOMINANT Only one mutated gene on one chrom. is
needed to display the disorder AUTOSOMAL RECESSIVE
Two copies of mutated gene must be present to display the disorder
X-Linked DOMINANT Mutations on the X chrom. that are dom.
X-Linked RECESSIVE (like hemophilia)
Pedigrees
A pedigree chart is a tool used to show all the known phenotypes of an organism and its ancestors…
Used in human genealogy study
Pedigrees
Let’s build one…
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