Dr. Ramesh GRU2L10.1 Codominance and Incomplete Dominance
Do Now! Directions: Answer the following questions. The trait for brown eyes is dominant to the trait for blue eyes. A man who is heterozygous for brown eyes has children with a woman who is heterozygous for brown eyes. 1.What are the parents genotypes? A)Mom B) Dad 2.Draw the cross between the two parents using a Punnett Square. 3.What are the genotypic and phenotypic ratios of the children?
Objective! The student will (TSW) discuss the difference between incomplete dominance and codominance while using Punnett Squares.
Why are we learning this?!
Why are we learning this?! DNA is the fabric of life that ties together all living things. Its role is absolutely vital to organisms daily functioning.
Incomplete Dominance Key Point #7: Incomplete dominance: In heterozygotes, the dominant and recessive alleles BLEND TOGETHER. Example: In carnation flowers, red (R) and white (r) are incompletely dominant.
Incomplete Dominance! RR rr Rr
Incomplete Dominance! Incomplete dominance occurs when heterozygous offspring show a blend of phenotypes from parents. Example: Red flower + White flower = Pink flower
Incomplete Dominance!
Incomplete Dominance! RR rr
Codominance!
Codominance! Codominance occurs when heterozygous offspring show both phenotypes of parents. (Usually in form of spots or stripes) Example: Red flower + White flower = Red & White Spotted flower
Codominance!
Codominance!
Codominance!
CHECK FOR UNDERSTANDING Voices at a Level Zero Mark your answers on your white board Raise your hand if you have questions
Check For Understanding! Answer the following question In rabbits, fur color is controlled by incomplete dominance. The allele for black is B and the allele for white is b. What is the genotype for a black bunny? BB
Check For Understanding! Answer the following question In rabbits, fur color is controlled by incomplete dominance. The allele for black is B and the allele for white is b. What is the genotype for a white bunny? bb
Check For Understanding! Answer the following question In rabbits, fur color is controlled by incomplete dominance. The allele for black is B and the allele for white is b. What is the genotype for a grey bunny Bb
Check For Understanding! Answer the following question In horses, coat color is due to codominance. The allele for brown is B and the allele for white is b. The spotted horse is heterozygous. What is its genotype? Bb
Check For Understanding! Answer the following question In horses, coat color is due to codominance. The allele for brown is B and the allele for white is b. What color is a horse who has a genotype of bb? White
Check For Understanding! Answer the following question In horses, coat color is due to codominance. The allele for brown is B and the allele for white is b. What color is a horse who has a genotype of Bb? Spotted (Brown and White)
Check For Understanding! Answer the following question CODOMINANCE OR INCOMPLETE DOMINANCE? Codominance
Check For Understanding! Answer the following question CODOMINANCE OR INCOMPLETE DOMINANCE? Codominance
Check For Understanding! Answer the following question CODOMINANCE OR INCOMPLETE DOMINANCE? = Incomplete Dominance
Check For Understanding! Answer the following question CODOMINANCE OR INCOMPLETE DOMINANCE? Codominance
Check For Understanding! Answer the following question CODOMINANCE OR INCOMPLETE DOMINANCE? Codominance
DIRECTIONS Voices at a Level Zero Complete the Guided Practice Answer in complete sentences Raise your hand if you have questions
Banana and Ice Cream
Co-Dominance Banana + Ice Cream TOGETHER
Incomplete Dominance Banana + Ice Cream BLEND
Incomplete Dominance Genotype RR (homozygous red) Rr (heterozygous) rr (homozygous white) Phenotype red pink white
Incomplete Dominance
Incomplete Dominance RR Rr rr
Incomplete Dominance
Incomplete Dominance In carnation flowers, color is an incompletely dominant trait. Red (R) is dominant over white (r). Create a Punnett square and cross two heterozygous carnations. Heterozygous= DIFFERENT Parent 1: Rr Parent 2: Rr
Guided Practice (GP) 1 Directions: In humans, tall (T) and short (t) are incompletely dominant. 1. Show the potential offspring of a heterozygous father and a homozygous recessive mother in a Punnett Square 2. Fill in percents for genotype and phenotypes. GENOTYPES: TT: Tt: tt: PHENOTYPES: Tall: Short: Medium
Guided Practice (GP) 2 Directions: In humans, dark skin (D) and light skin (d) are incompletely dominant. 1. Show the potential offspring of a homozygous dominant and a homozygous recessive plant in a Punnett square. 2. Fill in percents for genotype and phenotype. GENOTYPES: PHENOTYPES:
Co-Dominance Key Point #8: In co-dominance, both alleles are dominant. In heterozygotes, both alleles are expressed EQUALLY. NOTICE ALL GENOTYPES HAVE CAPITAL LETTERS BECAUSE ALL TRAITS ARE DOMINANT, NOTHING IS RECESSIVE! Example: Sickle cell anemia in humans AA = normal cells SS = sickle cells AS = half of each
Check yo self on Codominance WARNING: This is the ONLY kind of inheritance where you use two DIFFERENT letters!!!!!!!! For all others you use the same letter, just capital and lower case.
Sickle Cell Anemia
Sickle cells easily get stuck in the circulatory system.
GP 3: Sickle Cell Anemia Having normal (A) and sickle (S) cells are codominant. 1. Show the potential offspring of a normal father and a heterozygous mother in a Punnett square. 2. Fill in percents for genotype and phenotype. GENOTYPES: AA: 50% AS: 50% SS: 0% A AA A A AA PHENOTYPES: Normal: 50% Some normal, some sickle: 50% Sickle Cell: 0% S AS AS
GP 4: Cow Coat Color In cows, color is co-dominant. 1. Show the potential offspring between a red bull (RR) and a white cow (WW). 2. Fill in percents for genotype and phenotype. GENOTYPES: PHENOTYPES:
DIRECTIONS Voices at a Level Zero Complete the Independent Practice Answer in complete sentences Raise your hand if you have questions
Independent Practice Which type, (1) Mendelian (normal), (2) incomplete dominance, or (3) codominance? 1. Rats can be white or have color. If you mate a homozygous dominant brown mouse with a white mouse, you get all brown mice. 2. A man with green eyes and a woman with brown eyes have a baby. The baby has eyes that are brown with bits of green in them. 3. In rabbits, if the genotype is BB it is black, WW is white and BW is grey.
Independent Practice Which type, (1) Mendelian (normal), (2) incomplete dominance, or (3) codominance? 1. Rats can be white or have color. If you mate a homozygous dominant brown mouse with a white mouse, you get all brown mice. Ans: Mendelian 2. A man with green eyes and a woman with brown eyes have a baby. The baby has eyes that are brown with bits of green in them. Ans: Codominance 3. In rabbits, if the genotype is BB it is black, WW is white and BW is grey.ans: Incomplete dominance
DIRECTIONS Voices at a Level Zero Complete the Exit Ticket Answer in complete sentences Raise your hand if you have questions
Exit Ticket! DIRECTIONS: Copy and answer the following questions. 1) What is the difference between codominance and incomplete dominance? 2) What color and genotype will the offspring have if a red flower (RR) reproduced with a white flower (rr) under incomplete dominance?