Gene Interaction and Epistasis Hair color is due to the presence of melanin. There are two types of melanin produced by melanocytes. One is eumelanin, which is responsible for black (homozygous), brown (heterozygous), and blond (recessive) hair colors. The other is pheomelanin, which is responsible for red hair color. During melanin synthesis, MCR1gene converts pheomelanin to eumelanin. However, a variant of the MCR1 gene (MCR1variant), prevents this conversion. A cross between a blond-haired mother and a red-haired father produced 100% brown-haired children. When they came of age, one child married a double heterozygote, and both were blessed with 7 children; 2 with black hair, 2 with brown hair, 1 with blond hair, and 2 with red hair. Using the 7-step method, determine the genotypes of the P1, the F1, and the F2s. BOX your answers (if handwritten) or HIGHLIGHT your answers (if encoded). STEP 1: ________________________________________________________ STEP 2: ________________________________________________________ STEP 3: ________________________________________________________ STEP 4: ________________________________________________________ STEP 5: ________________________________________________________ STEP 6: ________________________________________________________ STEP 7: P1: __________________ x _____________________ blond red F1: ______________ brown F2: 2 black ______________________ 2 brown ______________________ 1 blond ______________________ 2 red ______________________
Gene Interaction and Epistasis
Hair color is due to the presence of melanin. There are two types of melanin produced by melanocytes. One is eumelanin, which is responsible for black (homozygous), brown (heterozygous), and blond (recessive) hair colors. The other is pheomelanin, which is responsible for red hair color. During melanin synthesis, MCR1gene converts pheomelanin to eumelanin. However, a variant of the MCR1 gene (MCR1variant), prevents this conversion.
A cross between a blond-haired mother and a red-haired father produced 100% brown-haired children. When they came of age, one child married a double heterozygote, and both were blessed with 7 children; 2 with black hair, 2 with brown hair, 1 with blond hair, and 2 with red hair.
Using the 7-step method, determine the genotypes of the P1, the F1, and the F2s. BOX your answers (if handwritten) or HIGHLIGHT your answers (if encoded).
STEP 1: ________________________________________________________
STEP 2: ________________________________________________________
STEP 3: ________________________________________________________
STEP 4: ________________________________________________________
STEP 5: ________________________________________________________
STEP 6: ________________________________________________________
STEP 7:
P1: __________________ x _____________________
blond red
F1: ______________
brown
F2: 2 black ______________________
2 brown ______________________
1 blond ______________________
2 red ______________________
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