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Dihybrid Cross Worksheet
- Set up a punnett square using the following information: ·∙ Dominate allele for tall plants = D ·∙ Recessive allele for dwarf plants = d ·∙ Dominate allele for purple flowers = W ·∙ Recessive allele for white flowers = w ·∙ Cross a homozygous dominate parent (DDWW) with a homozygous recessive parent (ddww) dw dw dw dw DW DdWw DdWw DdWw DdWw DW DdWw DdWw DdWw DdWw DW DdWw DdWw DdWw DdWw DW DdWw DdWw DdWw DdWw
x All offspring will be heterozygous for both traits (DdWw) and their phenotype will be Tall and purple flowers.
- Set up a punnett square using the following information: ·∙ Dominate allele for black fur in guinea pigs = B ·∙ Recessive allele for white fur in guinea pigs =b ·∙ Dominate allele for rough fur in guinea pigs = R ·∙ Recessive allele for smooth fur in guinea pigs = r ·∙ Cross a heterozygous parent (BbRr) with a heterozygous parent (BbRr) BR Br bR br BR BBRR BBRr BbRR BbRr Br BBRr BBrr BbRr Bbrr bR BbRR BbRr bbRR bbRr br BbRr Bbrr bbRr bbrr
- Using the punnett square in question #3: a. What is the probability of producing guinea pigs with black, rough fur? 9/16 = 56%
Possible genotype(s)? BBRR BBRr BbRR BbRr b. What is the probability of producing guinea pigs with black, smooth fur? 3/ Possible genotype(s)? BBrr Bbrr c. What is the probability of producing guinea pigs with white, rough fur? 3/ Possible genotype(s)? bbRR bbRr d. What is the probability of producing guinea pigs with white, smooth fur? 1/ Possible genotype(s)? bbrr
- Set up a punnett square using the following information: ·∙ Dominate allele for purple corn kernels = R ·∙ Recessive allele for yellow corn kernels = r ·∙ Dominate allele for starchy kernels = T ·∙ Recessive allele for sweet kernals = t ·∙ Cross a homozygous dominate parent with a homozygous recessive parent RRTT x rrtt rt rt Rt rt RT RrTt RrTt RrTt RrTt RT RrTt RrTt RrTt RrTt RT RrTt RrTt RrTt RrTt RT RrTt RrTt RrTt RrTt
- Using the punnett square in question #5: a. What is the probability of producing purple, starchy corn kernels? 16/ Possible genotype(s)? RrTt b. What is the probability of producing yellow, starchy corn kernels? 0
Possible genotype(s)? nnBB nnBb d. What is the probability of producing a wolf with a black coat with blue eyes? 1/ Possible genotype(s)? nnbb
- A tall pea plant with terminal flowers (flowers on the ends of the stems) is crossed with a short plant that has axial flowers. All 72 offspring are tall with axial flowers. This is a dihybrid cross with the height and flower position traits showing independent assortment.
a. Name the dominant and recessive alleles. Dominant: Tall (T) Recessive: Short (t) Axial (A) terminal (a)
b. Give the genotypes of the parents and offspring in this cross. Tall terminal x short axial TTaa x ttAA
tA tA tA tA Ta TtAa TtAa TtAa TtAa Ta TtAa TtAa TtAa TtAa Ta TtAa TtAa TtAa TtAa Ta TtAa TtAa TtAa TtAa
x All offerspring are TtAa c. Predict the F2 offspring when the tall-‐axial F1's are allowed to self pollinate. TtAa X TtAa
9 tall axial : 3 Tall terminal: 3 short axial: 1 short terminal
TA Ta tA ta TA TTAA TTAa TtAA TtAa Ta TTAa TTaa TtAa Ttaa tA TtAA TtAa ttAA ttAa ta TtAa Ttaa ttAa ttaa
- Suppose a white, straight haired guinea pig mates with a brown, curly-‐haired animal. All five babies in their first litter have brown fur, but three are curly and two have straight hair. The second litter consists of six more brown offspring, where two are curly and four are straight haired. a. Assuming curly is dominant to straight, what are the genotypes of the parents and the offspring?
- brown dominate to white ( all babies brown) Hair color brown dominate = B Hair color white recessive = b Curly = T Straight = t Parent Genotypes: white straight haired = bbtt Brown curly haired = BBTt ( we know this because no white guinea pigs were produced) BT Bt BT Bt bt BbTt Bbtt BbTt Bbtt bt BbTt Bbtt BbTt Bbtt bt BbTt Bbtt BbTt Bbtt bt BbTt Bbtt BbTt Bbtt
b. What is the probability of getting two female guinea pigs with straight hair in a row? .50 x .50 = .25͙͙. 25% chance of getting two female guinea pigs with straight hair in a row.
CR CcRr CcRr CcRr CcRr
F2: Genotypes CcRr x CcRr CR Cr cR cr CR CCRR CCRr CcRR CcRr Cr CCRr CCrr CcRr Ccrr cR CcRR CcRr ccRR ccRr cr CcRr Ccrr ccRr ccrr
b. Carry out to the F2 generation a cross between a homozygous plain red bird and its homozygous checkered brown mate. F1: ccRR x CCrr Cr Cr Cr Cr cR CcRr CcRr CcRr CcRr cR CcRr CcRr CcRr CcRr cR CcRr CcRr CcRr CcRr cR CcRr CcRr CcRr CcRr
F2: CcRr x CcRr
CR Cr cR cr CR CCRR CCRr CcRR CcRr Cr CCRr CCrr CcRr Ccrr cR CcRR CcRr ccRR ccRr cr CcRr Ccrr ccRr ccrr
c. A plain brown female pigeon laid five eggs. The young turned out to be: 2 plain red, 2 checkered red, and 1 checkered brown. Describe the father pigeon. Give the genotypes of all birds in this cross. Could any other types of offspring have been produced by this pair? Mother: ccrr Children: plain red ʹ ccRr or ccRR Checkered red ʹ CCRR or CcRr or CCRr or CcRR Checkered brown ʹ CCrr or CcRR
Father must be CcRr because the recessive traits are visible in his offspring. Yes, plain brown
