12.1 Basic Patterns of Human Inheritance

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Chapter 12. 12.1 Basic Patterns of Human Inheritance. Recessive Genetic Disorders. A recessive trait is expressed when the individual is homozygous recessive for the trait. Chapter 12. 12.1 Basic Patterns of Human Inheritance. Cystic Fibrosis. - PowerPoint PPT Presentation

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  • 12.1 Basic Patterns of Human InheritanceChapter 12Recessive Genetic DisordersA recessive trait is expressed when the individual is homozygous recessive for the trait.

  • Cystic Fibrosis Affects the mucus-producing glands, digestive enzymes, and sweat glands Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat. Without sufficient chloride ions in the cells, a thick mucus is secreted. 12.1 Basic Patterns of Human InheritanceChapter 12

  • AlbinismCaused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes White hairVery pale skinPink pupils12.1 Basic Patterns of Human InheritanceChapter 12

  • Tay-Sachs Disease Caused by the absence of the enzymes responsible for breaking down fatty acids called gangliosides Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration. 12.1 Basic Patterns of Human InheritanceChapter 12

  • Galactosemia Recessive genetic disorder characterized by the inability of the body to digest galactose. 12.1 Basic Patterns of Human Inheritance

  • Dominant Genetic Disorders Huntingtons disease affects the nervous system. Achondroplasia is a genetic condition that causes small body size and limbs that are comparatively short.12.1 Basic Patterns of Human InheritanceChapter 12

  • 12.1 Basic Patterns of Human InheritanceChapter 12

  • PedigreesA diagram that traces the inheritance of a particular trait through several generations 12.1 Basic Patterns of Human InheritanceChapter 12

  • Inferring Genotypes Knowing physical traits can determine what genes an individual is most likely to have. Predicting Disorders Record keeping helps scientists use pedigree analysis to study inheritance patterns, determine phenotypes, and ascertain genotypes.12.1 Basic Patterns of Human InheritanceChapter 12

  • 12.2 Complex Patterns of InheritanceIncomplete DominanceThe heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes. (both alleles are blended)Chapter 12

  • CodominanceBoth alleles are expressed in the heterozygous condition. (both alleles are seen at the same time)12.2 Complex Patterns of InheritanceChapter 12

  • Sickle-cell Disease Changes in hemoglobin cause red blood cells to change to a sickle shape. People who are heterozygous for the trait have both normal and sickle-shaped cells. Sickle cellNormal red blood cell7766x12.2 Complex Patterns of InheritanceChapter 12

  • Multiple AllelesBlood groups in humans ABO blood groups have three forms of alleles.12.2 Complex Patterns of InheritanceChapter 12

  • Coat Color of RabbitsMultiple alleles can demonstrate a hierarchy of dominance.In rabbits, four alleles code for coat color: C, cch, ch, and c.12.2 Complex Patterns of InheritanceChapter 12

  • Coat Color of Rabbits Light grayDark grayHimalayanAlbinoChinchilla12.2 Complex Patterns of InheritanceChapter 12

  • EpistasisVariety is the result of one allele hiding the effects of another allele. No dark pigment present in furDark pigment present in fureebbeeB_E_bbE_B_12.2 Complex Patterns of InheritanceChapter 12

  • Sex Determination Sex chromosomes determine an individuals gender. 12.2 Complex Patterns of InheritanceChapter 12

  • Sex-Linked TraitsGenes located on the X chromosome Red-green color blindness Hemophilia 12.2 Complex Patterns of InheritanceChapter 12

  • Polygenic TraitsPolygenic traits arise from the interaction of multiple pairs of genes. 12.2 Complex Patterns of InheritanceChapter 12

  • Environmental Influences Environmental factorsDiet and exerciseSunlight and waterTemperature12.2 Complex Patterns of InheritanceChapter 12

  • Twin StudiesHelps scientists separate genetic contributions from environmental contributions Traits that appear frequently in identical twins are at least partially controlled by heredity.Traits expressed differently in identical twins are strongly influenced by environment.12.2 Complex Patterns of InheritanceChapter 12

  • Karyotypemicrograph in which the pairs of homologous chromosomes are arranged in decreasing size.12.3 Chromosomes and Human HeredityKaryotype StudiesImages of chromosomes stained during metaphase Chromosomes are arranged in decreasing size to produce a micrograph. Chapter 12

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