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Human Genetics

Mutations, Sex-linked traits, Disorders, Pedigrees. Human Genetics. 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…

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Human Genetics

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  1. Mutations, Sex-linked traits, Disorders, Pedigrees Human Genetics

  2. 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)

  3. 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)

  4. 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

  5. What’s a Mutation? • Chromosomal Mutations • 1. Deletion • Part of chromosome is missing

  6. What’s a Mutation? • Chromosomal Mutations • 1. Deletion • Part of chromosome is missing • 2. Duplication • Part of chrom. is included twice

  7. 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

  8. 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-homologouschrom. exchange portions

  9. 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

  10. What’s a Mutation? • Some mutations are significant and severe, some are less so, some are never noticed… • Consider the car…

  11. 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 Xchrom.

  12. Sex-Linked Traits • Hemophilia (sex-linked recessive) • Females/Males: • XHXH Female, clots • XHXhFemale, clots (carrier) • XhXhFemale, can’t clot • XHy Male, clots • Xhy Male, can’t clot

  13. 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…

  14. Normal Male Karyotype: 22 sets of autosomes, 1 set of sex chromosomes

  15. 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 Xchrom. that are dom. • X-Linked RECESSIVE (like hemophilia)

  16. 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

  17. Pedigrees • Let’s build one…

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