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-G thesunwashotbuttheoldmandidnotgethishat

What’s a Mutation?  Chromosomal Mutations  1. DeletionDeletion  Part of chromosome is missing

What’s a Mutation?  Chromosomal Mutations  1. DeletionDeletion  Part of chromosome is missing  2. DuplicationDuplication  Part of chrom. is included twice

What’s a Mutation?  Chromosomal Mutations  1. DeletionDeletion  Part of chromosome is missing  2. DuplicationDuplication  Part of chrom. is included twice  3. InversionInversion  Part of chrom. is reversed from usual direction

What’s a Mutation?  Chromosomal Mutations  1. DeletionDeletion  Part of chromosome is missing  2. DuplicationDuplication  Part of chrom. is included twice  3. InversionInversion  Part of chrom. is reversed from usual direction  4. TranslocationTranslocation  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:  X H X H Female, clots  X H X h Female, clots (carrier)  X h X h Female, can’t clot  X H yMale, clots  X h yMale, 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)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… Let’s build one…