We are working with two independent (non-linked) genes in a fictitious pine tree

Question

We are working with two independent (non-linked) genes in a fictitious pine tree that control the length of trichomes (hairlike

structures) on the cone scales and needle length. Let’s suppose that prior cross-pollination studies suggested that the allele for hairy

(hc) cone scales was recessive to wildtype (+, smooth) scales and that the allele for short (sn) needles was recessive to wildtype (+, long)

needles.

Construct a Punnett rectangle to predict the offspring phenotypic ratio that you would expect for a cross between a pine tree that is

heterozygous for both traits and a pine tree that is heterozygous for cone trichomes but has short needles. Show your work.

Explanation / Answer

Setting: two independent (non-linked) genes
Trait 1: length of trichomes (hairlike structures) on the cone scales
Trait 2: needle length
Smooth cone scales is dominant over hairy. (Hairy=cc)
Long needle length is dominant over short. (Short=nn)

Applying the Mendelian Laws of Inheritance (mainly Segregation, Independent Assortment and Dominance), we get
Pine tree that is heterozygous for both traits = CcNn
Possible gametes = CN, Cn, cN, cn
Pine tree that is heterozygous for cone trichomes but has short needles = Ccnn
Possible gametes = Cn, cn
Possible offsrpings = CCNn, CCnn, CcNn, Ccnn, CcNn, Ccnn, ccNn, ccnn
Phenotype = 3 Smooth & Long, 3 Smooth & Short, 1 Hairy & Long, 1 Hairy & Short
Punnett rectangle to predict the offspring phenotypic ratio that you would expect for a cross between the pair =
.....// CN // Cn // cN // cn
Cn//CCNn // CCnn // CcNn // Ccnn
cn//CcNn // Ccnn // ccNn // ccnn

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.