Beyond Dominant and Recessive NonMendelian Inheritance Chapter 10

Beyond Dominant and Recessive Non-Mendelian Inheritance Chapter 10 -3 (eye book)

This means traits that don’t fit Mendel’s patterns of inheritance ?

Co - Dominance • In co dominance, there are three phenotypes. • For this type of inheritance, there are two dominant traits. • This time, both dominant traits show in the heterozygous phenotype – For example: The two dominant traits of this type of fowl are white and black. The heterozygous phenotype appears speckled

Co Dominance • The way we write alleles for this type of inheritance is with two different capital letters. • Each dominant trait gets its own letter • The heterozygous genotype gets both capital letters Red = RR Stripes = RW White = WW

Practice 1. Look at all the cows. What are all the phenotypes? 2. Which two traits are dominant, which is the mixed trait? 3. What notation will you use to represent… a) The brown cow? BB b) The white cow? WW c) The speckled? BW

Incomplete Dominance (Also called – Intermediate inheritance) • In incomplete dominance, there are three phenotypes. The heterozygous phenotype is halfway in between the two other phenotypes • This is referred to as blending

Incomplete Dominance (Also called – Intermediate inheritance) • Since one phenotype is not dominant over the other, the homozygous phenotypes are both considered dominant. Red = Dominant Pink = Blended White = Dominant

Incomplete Dominance (Also called – Intermediate inheritance) • The way we write alleles for this type of inheritance is with letters and superscripts. • We pick one letter to represent the trait – (ex – C for color) • We use superscripts to represent the expression of the trait – (ex – two different capital letters, for each dominant trait) Red = CRCR Pink = CRCW White = CWCW

Practice 1. Look at all the fish. What are all the phenotypes? 2. Which two traits are dominant, which is the blended trait? 3. What notation will you use to represent… a) The blue fish? b) The red fish? c) The purple fish? CB CB C RC R C RC B

Lethal Allele When an organism with a particular genotype does not survive Example: Mexican Hairless Dogs H H h HH Hh hh Dogs with the genotype HH do not develop and are never born. The resulting phenotype ratio is 2 hairless : 1 with hair

Lethal Allele • This is like Mendelian genetics because: – There are only two phenotypes – We use the same letter in capital and lower case • This is different than Mendelian genetics because: – You never get a 3: 1 ratio – you get a 2: 1 ratio instead

Multiple Alleles • Some traits have more than two possible alleles. • Organisms still get two alleles, one from each parent • This increases the number of possible genotypes and phenotypes

Multiple Alleles • Human blood type is a good example of a trait with multiple alleles. • There are 4 different blood types: A, B, AB or O, which refer to a specific carbohydrate on the red blood cells Phenotype (Blood type) Genotype O IO IO A IAIA or IAIO B IBIB or IBIO AB IA IB

Copy this flowchart into your notes!!! 3 phenotypes 2: 1 ratio Lethal Start All other ratios Mendelian Blending Incomplete Dominance Both traits show Codominance

White Horses Brown Horses 1. What type of inheritance is shown? Tan Horses 2. What gene symbols (letters) should you use to represent each phenotype? 3. What parent cross led to this population? Prove it with a Punnett Square All Tan Horses

Tan puppies Brindle (striped tan and brown) puppies brown puppies 1. What type of inheritance is shown? 2. What gene symbols (letters) should you use to represent each phenotype? 3. What parent cross led to this population? Prove it with a Punnett Square Half tan puppies and half brindle puppies

More Practice A) 100% white fish 33% white fish B) 100% red fish 1. Mode of Inheritance 2. Gene Symbol (Letters) for each phenotype 3. Parent cross that gave us population A) B) C) C) 66% red fish &

Population 1 – 100% White fish Warm Up Population 3 – 50% Red fish and 50% striped fish Population 2 – 100% Striped fish 1. What type of inheritance is shown? all three have the same: ( Mendelian / Incomplete dominance / Co-dominance / Lethal) (Use your flow chart from yesterday to find out!!!) 2. What are three phenotypes present? (Look at the fish, and write down the three types you see) 3. What gene symbols (letters) should you use to represent each phenotype? (Use your notes from yesterday to find out!!!) 4. What are the genotypes of the fish in each population? (Match your answer from #3 to each population of fish)

MOI Table: • Mendelian and Lethal Parental Crosses: RR x RR Rr x Rr RR x Rr Rr x rr RR x rr rr x rr • Non Mendelian Parental Crosses: RR x RR RW x RW RR x RW RW x WW RR x WW WW x WW CW CW x C W CW CW CR x C W CR C W CW x C W CR , C W CR X C R CR CW CW x C R CR X C R CR NOTE – All Examples are for Red and White…you can use ANY letters