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Mendelian Inheritance of Human Traits

Mendelian Inheritance of Human Traits. Section 12.1. Pedigrees. A graphic representation of genetic inheritance A set of symbols (see chart on page 309) Male/Female Affected by trait or not Family relationships Carrier-heterozygous . Simple Recessive Heredity.

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Mendelian Inheritance of Human Traits

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  1. Mendelian Inheritance of Human Traits Section 12.1

  2. Pedigrees • A graphic representation of genetic inheritance • A set of symbols (see chart on page 309) • Male/Female • Affected by trait or not • Family relationships • Carrier-heterozygous

  3. Simple Recessive Heredity • Most genetic disorders are caused by recessive alleles • Individual must be homozygous recessive to have disorder • Cystic fibrosis (CF) • Tay-Sachs disease • Phenylketonuria (PKU)

  4. Simple Dominant Heredity Only a single dominant allele is necessary for characteristic Cleft chin Dimples Freckles Widow’s peak Detached earlobes Six fingers Hair on the middle section of fingers Huntington’s disease

  5. When Heredity Follows Different Rules Section 12.2

  6. Incomplete Dominance Appearance of a third phenotype

  7. Codominance Both alleles are expressed equally

  8. Multiple alleles Traits controlled by more than two alleles

  9. Sex determination Autosomes: 22 pairs of homologous chromosomes in humans Sex chromosomes: XY (male) XX (female)

  10. Sex-linked inheritance Traits controlled by genes located on sex chromosomes Written as superscripts on X & Y

  11. Polygenic inheritance Inheritance pattern of a trait that is controlled by two or more genes May be on the same or different chromosomes Each gene may have two or more alleles Use upper & lower case letters Range of variability/phenotypes

  12. External Influences Genetic makeup determines only the potential to develop and function Temperature Nutrition Light Chemicals Infectious agents

  13. Internal Influences Sex influenced expressions-hormones Age

  14. Complex Inheritance of Human Traits Section 12.3

  15. Codominance Sickle-cell amemia Changes shape of red blood cell Results in several blood disorders

  16. Multiple Alleles Phenotype Genotype A AA or AO B BB or BO AB AB O OO Blood types

  17. Sex-Linked Traits Red-green color blindness Hemophilia

  18. Polygenic Inheritance Skin color Height

  19. Changes in Chromosome Numbers Nondisjunction Karyotype–chart of chromosome pairs Down Syndrome-Trisomy 21 Abnormal numbers of sex chromosomes

  20. Gene Frequency Activity andLINCS Tables Assignment for Chapter 12 Codominant allele Incomplete dominance Multiple allele Polygenic inheritance

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