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…