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Genetic Exceptions & Inheritance Patterns: Unraveling Complex Traits

Explore exceptions to Mendel's principles like incomplete dominance, codominance, blood types, and polygenic inheritance. Dive into how genetics and environmental influences shape our traits. Unravel the complexities of sex-linked traits and chromosomal mutations.

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Genetic Exceptions & Inheritance Patterns: Unraveling Complex Traits

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  1. Exceptions to Mendel’s Principles • Incomplete Dominance or Blending Inheritance • – When an organism is heterozygous for a trait and both genes are expressed but not completely.

  2. Example: Snap Dragon Flowers

  3. Codominance • When 2 different alleles are present and both alleles are expressed. • Example: Dalmatians • Dalmatians that are black and white have an allele for black and an allele for white • If a 2 Dalmatians that are black and white mate they will only have a 50% chance of having a black and white Dalmatian

  4. Bloodtypes • Blood types vary and your immune system recognizes your own blood type as being self. Other blood types are recognized as non-self. • Antigens are the markers on the cell that the immune system “looks” for to identify the cell.

  5. Antibody and Antigens • Antibodies are chemicals that are a part of the immune system that attaches to the antigens. • The antigen-antibody complex sends a signal to the immune system that something does not belong. The immune system tries to kill and remove the item.

  6. Antibody Antigen

  7. Bloodtypes Antigens & Antibodies

  8. Bloodtype Alleles • Allele IA produces antigen A • Allele IB produces antigen B • Allele i produces no antigen. 

  9. Codominance and Bloodtypes • Blood types are an example of codominance. • Both alleles are fully expressed (both antigens appear completely when the genotype is heterozygous). • Example: Bloodtype AB

  10. Exception to Independent Assortment Linked Traits = • Genes that are next to each other on the same chromosome have a greater chance of being passed on together. • Red hair and freckles

  11. Linkage Maps – • Created from linked relationships • Based on the number of “crossovers” we can determine the order of the genes and their relative distance to each other. • Greater % of cross over = farther apart b and cn =9%, cn and vg = 9.5%, b and vg = 18.5%

  12. Sex Linked or X-Linked Traits • Traits that are more often found on one sex than the other is said to be sex linked. • If the gene on an X chromosome is recessive it would take two of those genes to show up on a female. While it would only take one gene for that trait to show up on the male (since he only has one X).

  13. Examples of Sex Linked Traits • Color Blindness • Hemophilia

  14. Exceptions to Principle of Segregation • Passing on of multiple chromosomes = nondisjunction • Polysomy = more than 2 genes/trait • examples: Down syndrome (extra #21 chromosome = trisomy)

  15. XXY = Klinefelter syndrome • XO = Turner syndrome (monosomy) • XXX = triple-X syndrome • Chromosomal mutations results in multiple or missing genes • examples: deletion and duplication

  16. Polygenic Inheritance • Several genes influence a character (trait) • May be scattered on different chromosomes or on the same chromosome • Examples: Hair color, weight, height, and eye, hair and skin color

  17. Environmental Influences • Phenotypes often depend on environmental conditions • examples: Hydrangea plants in acidic soil have blue flowers and those in basic soil have pink flowers • artic fox fur, Himalayan rabbit fur, and Siamese cat fur color • Human height and skin color

  18. Sex-influenced • traits expressed differently in the two sexes. • autosomal (not on the sex chromosomes) • male-pattern baldness • Sex-limited • expressed in only one sex. • example lactation, or milk production. • genes in both males and females, only lactating females express these genes (LH –hormone)

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