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Heredity not following the Rules

This text explains the concepts of incomplete dominance, codominance, and multiple alleles in heredity, using examples such as snapdragons, Dominique chickens, ABO blood typing, and coat color in rabbits. It also discusses polygenic inheritance and includes quizzes to test understanding.

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Heredity not following the Rules

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  1. Heredity not following the Rules

  2. Incomplete dominance • A heterozygous condition in which both alleles are partially expressed, often producing an intermediate or blended phenotype (which is different than either of the homozygous forms). Snapdragons

  3. Incomplete dominance Both traits are "weak" and not strong enough alone, so they blend their strengths to make a new color. Snapdragons

  4. In Incomplete DOMINANCE, use the SAME letters since they both are weak! Incomplete dominance RR R’R’ RR’ RR RR’ RR’ R’R’

  5. Incomplete dominance • Palomino horses are a cross between a chestnut horse and a cremello (white) color horse. • Practice the cross using a Punnet Square. H’ H’ H H

  6. Codominance • Codominance –Neither phenotype is dominant. Instead, the individual expresses both phenotypes. Co – both are dominant enough to be expressed!! Dominique chickens

  7. In CODOMINANCE, use DIFFERENT letters since they both are strong! Codominance BB - Black WW - White BW - Black and White W W Predict the outcome if BOTH chickens are dominique (black and white) ???? Cross a black chicken with a white chicken and what to you get if the traits are CODOMINANT? B B

  8. Codominance BB - Black WW - White BW - Black and White B W BB=1 B BW=2 W WW=1

  9. Codominance • Another example of codominance is ABO blood typing. The blood types A and B are codominant to each other; however, type O is actually recessive to A and B.

  10. Codominance BB or BO OO AB AA or AO When both alleles exist, both are present!

  11. Which group is the universal recipient? Which group is the universal donor? Codominance Universal recipient Universal donor

  12. AB? Practicing Blood Types • A man of blood type AA marries a woman with blood type AB. What is the chance they will have a child with type AB blood? A B A A

  13. There could be 2 genotypes for the man: BB or BO O? Practicing Blood Types #2 • A man of blood type B marries a woman with blood type O. What is the chance they will have a child with type O blood? O O O O B B 50% 0% B O

  14. Multiple Alleles • An individual can only have 2 genes thus 2 alleles for a trait, but there could be more than 2 alleles present in a population. This type of inheritance is known as multiple alleles. Why can you only have 2 genes for each trait? Because… you only have 2 of each type of chromosome!!

  15. Multiple Alleles - examples • In Blood typing, there are 2 possible alleles (genes) that could could inherit – A, B, and O, but you can only inherit 2 of them. In this case, blood typing is also a trait that has multiple alleles. • Coat color in rabbits is inherited as a series of multiple alleles.

  16. Multiple Alleles - examples How many alleles are there for rabbit coat color? 4

  17. Multiple Alleles - examples Why is dark gray a capital C? • What are all of the possible genotypes for a • dark-gray coated rabbit? (4) • CC Ccch Cch Cc • chinchilla rabbit (3) • cchcch cchchcchc • Himilayan rabbit(2) • chch chc • White rabbit (1) • cc

  18. Multiple Alleles - examples • Predict the phenotype for a rabbit with a cchch. • Chinchilla • Is it possible to obtain a white rabbit if one parent is white and the other is chinchilla? • Yes. Only if the chichilla is cchc

  19. Polygenic Inheritance • Polygenic inheritance is the inheritance pattern of a trait that is controlled by two or more genes. The genes may be on the same chromosome or on different chromosomes. • Height in humans • Skin color

  20. Polygenic Inheritance Skin color

  21. POPQUIZ!! (Just kidding) • A roan cow is the product of a red cow and a white cow. What type of inheritance is exhibited? • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic B

  22. POPQUIZ!! • Curly headed people have the genotype HH, while straight headed people have the genotype hh. A wavy headed person is heterozygous. What type of inheritance does this exhibit? • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic C

  23. POPQUIZ!! • How well a person performs on an IQ test is controlled by multiple genes. Which of the following types of inheritance does this exhibit? • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic F

  24. POPQUIZ!! • Hair loss is a trait caused by a gene located on the X chromosome. This trait would be considered - • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic D

  25. POPQUIZ!! • Kim’s has always wondered why her 2nd toe is longer than her first. She recently discovered that it is a dominant trait. This trait is considered to exhibit - • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic A

  26. BTW

  27. POPQUIZ!! • Here is an easy one! Blood types fall under the category of which type of inheritance? • Complete dominance • Codominance • Incomplete dominance • Sex-linked • Multiple alleles • Polygenic E A B HEE HEE

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