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COMPLEX INHERITANCE

COMPLEX INHERITANCE. Chapter 12- Simplified Version. CHROMOSOMES:. Humans have 23 pairs of chromosomes One pair is sex chromosome: XX in females, XY in males It is the presence of Y chromosome that determines maleness. Y CHROMOSOME.

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COMPLEX INHERITANCE

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  1. COMPLEX INHERITANCE Chapter 12- Simplified Version

  2. CHROMOSOMES: • Humans have 23 pairs of chromosomes • One pair is sex chromosome: • XX in females, XY in males • It is the presence of Y chromosome that determines maleness.

  3. Y CHROMOSOME • Does not have a homologous partner, and does not experience recombination during meiosis • Y chromosome a son inherits from his father is identical to Y chromosome his father inherited from his father (grandfather) • This can be used to establish paternity

  4. X-LINKED GENES • Located on X chromosome • Disorders inherited on X chromosome are called X-linked disorders • More common in males than in females

  5. INCOMPLETE DOMINANCE • EX: hair type • Heterozygotes have a phenotype intermediate between homozygous dominant and homozygous recessive

  6. CODOMINANT TRAIT • EX: ABO blood type • Both maternal and paternal alleles contribute equally and separately to the phenotype

  7. POLYGENIC TRAITS • Traits that are influenced by additive effects of multiple genes • Show a normal distribution in the population

  8. MULTIFACTORIAL INHERITANCE • A persons phenotype is determined by both his or her genotype at a number of different genes as well as by environmental influence • EX: human height, cardiovascular disease, and depression

  9. EXTRA CHROMOSOMES • Some genetic disorders result from having a chromosome number that differs from the usual 46 • EX: down syndrome (trisomy 21) has an extra copy of chromosome 21

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