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Non - Mendelian Genetics

Non - Mendelian Genetics. Patterns of Inheritance that don ’ t quite follow Mendel ’ s laws. Many traits, however, are inherited through more complex patterns Incomplete Dominance Polygenic Inheritance Multiple alleles/ Codominance Sex Linkage. Non-Mendelian Genetics.

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Non - Mendelian Genetics

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  1. Non - Mendelian Genetics Patterns of Inheritance that don’t quite follow Mendel’s laws

  2. Many traits, however, are inherited through more complex patterns Incomplete Dominance Polygenic Inheritance Multiple alleles/Codominance Sex Linkage Non-Mendelian Genetics • Mendel’s pea experiments displayed simple inheritance patterns

  3. Incomplete Dominance • “Degrees” of Dominance • Allele forms mix together to give an intermediate appearance • One allele does NOT completely mask the other • Note: Both homozygous forms are designated by distinct capital letters R = allele for red flowers W = allele for white flowers red x white ---> pink RR x WW ---> 100% RW Incomplete Dominance

  4. Polygenic Inheritance • Traits that result from the combine actions of many genes and environmental factors • EX: skin color, eye color, common diseases such as heart disease

  5. Today’s activity • To explore how a common polygenic disease may be inherited in a family using a pedigree chart

  6. Pedigrees • A diagram showing the inheritance of traits within a family

  7. Codominance • Multiple allele forms • A and B are dominant over O, but “Co” dominant with each other.

  8. ABO Blood System • Notation use capital letter “I” to show domiance over “i” and superscripts to show codominance.

  9. ABO Blood System • Blood type is determined by antigens (markers) on the outside of the cells • If antigens are mixed incorrectly, they react with antibodies which cause blood to clot.

  10. Sex-linked Cross • In Humans, 22 pairs of autosomes, 1 “pair” of sex chromosomes • The genes on located on X or Y chromosomes (usually X) are said to be linked to the chromosome. • Recessive sex-linked traits appear more often in males because there are no heterozygotes to carry or hide the trait.

  11. Sex-linked Cross • Genes are located on chromosomes • In Humans 22 pairs of autosomes, 1 “pair” of sex chromosomes • The genes on located on X or Y chromosomes (usually X) are said to be linked to the chromosome. • Recessive sex-linked traits appear more often in males because there are no heterozygotes to carry or hide the trait. Mom: XHXh Dad: XhY X

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