E p is od e T h r e e : N o n - M ed ellian Inheritance Here are some ground rules that you should ALWAYS follow when tackling an Inheritance Problem: 1. Define the Alleles in question - you must state which symbol represents which allele Make sure that you use the proper notation for the inheritance pattern of the trait 2. State the Genotypes of the Parents 3. State the possible gametes produced by each parent 4. Create a Punnett Square 5. Answer the Question - Report Genotypic Ratios as a fraction - Report Phenotypic Ratios as a percentage
(I) Problems with Multiple Alleles Make sure that you define all the alleles involved and include an Order of Dominance! 1. Eye colour in cats is determined by multiple alleles. Green colour is dominant over yellow which is dominant over orange which in turn is dominant over red. A green eyed cat and a yellow eyed cat mate and have green eyed, yellow eyed and red eyed kittens. What are the possible genotypes of the parent cats?
AMBIGUOS CASE WARNING! 2. Eye colour in cats is determined by multiple alleles. Green colour is dominant over yellow which is dominant over orange which is then dominant over red. A green eyed cat and a yellow eyed cat mate and have green eyed, yellow eyed and orange eyed kittens. What are the possible genotypes of the parent cats?
(II) Mixed Bag Two Trait Inheritance Problems Please pay attention to the Notation that you use to represent alleles here. If the question does not mention the inheritance pattern that a trait follows, it is assumed that the trait follows a Mendellian Inheritance pattern. 1. Baldness is a recessive sex linked trait. Brown hair is dominant over Blond hair. A balding, brown haired man whose mother had blond hair and a blond haired woman who carries the baldness allele have a daughter. What is the probability that their daughter will be blond haired and balding?
2. Brown fur is partially dominant over grey fur. The heterozygous combination produces black fur. Shaggy fur and Short Fur are co dominant. If an animal with black shaggy fur is crossed with an animal with grey short fur, what will the phenotypic ratio of the offspring be?
3. Anemia is a recessive sex linked blood disorder. Blood type is determined by multiple alleles and a pattern of co dominance. An anemic Father and a non affected Mother have a son. If the Father has type AB blood and the Mother has type O blood, what are the chances that their son is non affected and has type B blood? (The mother carries the allele for anemia)
(III) Polygenic Inheritance (Be careful here!) This situation is unique as the trait is based on the expression of more than one gene. Pay close attention as this method and interpretation is different than the inheritance problems that we have encountered thus far. You may need a calculator and some working knowledge about the rules of probability. 1. Skin colour is determined by the expression of 3 genes. Each gene, when expressed, produces the protein Melanin which darkens skin pigment. Each gene has two alleles. Homozygous dominant genotypes cause the gene to be fully expressed and produce a maximum amount of melanin. Heterozygous genotypes cause the gene to be partially expressed producing some melanin. Homozygous recessive genotypes result in minimal production of melanin by the gene. Two parents are heterozygous for all three of the skin colour genes. What is the probability that their children will have a LIGHTER skin colour than them?