Dihybrid Cross Problem Problem You are to predict

Dihybrid Cross Problem

Problem • You are to predict the types and possible ratios of traits in the offspring resulting from the cross between a male and female pig. • In pigs, curly tails (C) are dominant over straight tails (c). Pink color (P) is dominant over gray (p). • A male pig who is heterozygous for both traits is crossed with a female pig that is homozygous recessive for tail type and heterozygous for color.

If you follow the necessary steps in solving genetic problems with Punnett Squares, your Punnett life will be a breeze for you. It is very important that you follow the necessary steps! 1. Determine how to assign letters to represent alleles. This was given to you: Curly tails is dominant over straight tail, so curly tail = C and straight tail = c Pink color is dominant over gray color, so pink = P and gray = p

2. Fill in the P 1 cross with the correct alleles: P 1: ____ x ____ Since the male pig is heterozygous for both traits, there will be one capital letter and on lowercase letter for each trait. Remember, it takes 2 letters (alleles) to represent each trait. The female pig is homozygous recessive for type of tail (2 lowercase letters) and heterozygous for color (one capital and one lowercase letter). P 1: _Cc. Pp_ x _cc. Pp_

3. Determine possible gamete combinations from each parent: Remember that you will need one allele from each parent for EACH trait. Male: Cc. Pp = CP, Cp, c. P, cp Female: cc. Pp = c. P and cp

4. Fill in the sides of the Punnett square with the parent allele combinations. Male CP c. P Female cp c. P cp Cp c. P cp

5. Complete the Punnett square by taking the letters that correspond with each box and bring them into the boxes. (Remember that capital letters always go on front of lower case letters since they dominate over them. ) Male CP c. P Female cp c. P cp Cp c. P cp

5. Complete the Punnett square by taking the letters that correspond with each box and bring them into the boxes. (Completed) Male Cp c. P cp Cc. PP Cc. Pp cc. PP cc. Pp Ccpp Cc. Pp ccpp c. P Cc. Pp Cc. PP cc. Pp cp Cc. Pp Ccpp Cc. Pp ccpp CP c. P Female cp

6. Punnett square results. There are two factors to examine: genotypes and phenotypes. PHENOTYPE = appearance CURLY and PINK: ____/16 STRAIGHT and PINK_______/16 CURLY and GRAY: ______/16 STRAIGHT and GRAY: _______/16 GENOTYPE RATIOS:

Summary • We can predict that when a male pig that is homozygous dominant for both curly tail and pink color is crossed with a female pig that is homozygous recessive for tail type and heterozygous for color, that you will get all curly-tailed pink babies!