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Patterns of Human Inheritance

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Complex Inheritance and Human Heredity Recessive Genetic Disorders A recessive trait is expressed when the individual is homozygous recessive for the trait. – PowerPoint PPT presentation

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Title: Patterns of Human Inheritance


1
Patterns of Human Inheritance
2
Complex Inheritance and Human Heredity
Recessive Genetic Disorders
  • A recessive trait is expressed when the
    individual is homozygous recessive for the trait.

3
Complex Inheritance and Human Heredity
Cystic Fibrosis
  • Affects the mucus-producing glands, digestive
    enzymes, and sweat glands
  • Chloride ions are not absorbed into the cells.
  • Without sufficient chloride ions in the cells, a
    thick mucus is secreted.

4
Complex Inheritance and Human Heredity
Albinism
  • Caused by altered genes, resulting in the absence
    of the skin pigment melanin in hair and eyes
  • White hair
  • Very pale skin
  • Pink pupils

5
Complex Inheritance and Human Heredity
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.

6
Complex Inheritance and Human Heredity
Galactosemia
  • Recessive genetic disorder characterized by the
    inability of the body to digest galactose.

7
Complex Inheritance and Human Heredity
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.

8
Complex Inheritance and Human Heredity
Basic Patterns of Human Inheritance
9
Human Genetics
  • Difficulties with human genetics
  • Takes a long time to reach reproductive maturity
  • Relatively few offspring
  • Unethical to arrange matings between
    individuals with desired genotypes
  • Pedigree a graphic representation of genetic
    inheritance, a families phenotypic history
  • Made up of set of symbols

10
Pedigree Analysis
Symbols
11
Pedigree Analysis
  • Family Trees
  • Generations are numbered on the left with roman
    numerals
  • Siblings are numbered in birth order

12
Pedigree Analysis
Complex Inheritance and Human Heredity
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.
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