Dihybrid Cross

Last updated
Save as PDF

Page ID: 63998

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

Alleles of the RSPO2 gene on chromosome 13 determine furnishings in dogs. The allele RSPO2¹⁶⁷, which has a 167 base pair insertion compared to the wild-type RSPO2⁺ allele, is dominantly associated with the presence of furnishings. Alleles of the KRT71 gene on chromosome 27 contribute to hair curl. A missense allele (KRT71^Trp) changes an arginine in the wild-type allele (KRT71⁺) to tryptophan and is dominantly associated with curly hair.

A. If a true-breeding dog with furnishings and non-curly hair is crossed with a true-breeding dog without furnishings with curly hair, what are the genotypes and phenotypes of the offspring (F₁ generation)?

B. Draw the 4 chromosomes with all alleles labeled as they might align in metaphase I of meiosis in the F₁.

C. What are the gamete genotypes of the F₁?

D. Draw a Punnett Square showing a cross between two F₁ offspring. What are the phenotype ratios of the F₂?

E. If the cross in the P generation (part A) was between a dog with furnishings and curly hair and a dog without furnishings or curly hair, would your answer to part C be different? Explain your reasoning.

Reference:

Cadieu E, Neff MW, Quignon P, Walsh K, Chase K, Parker HG, Vonholdt BM, Rhue A, Boyko A, Byers A, Wong A, Mosher DS, Elkahloun AG, Spady TC, André C, Lark KG, Cargill M, Bustamante CD, Wayne RK, Ostrander EA. Coat variation in the domestic dog is governed by variants in three genes. Science. 2009 Oct 2;326(5949):150-3. doi: 10.1126/science.1177808. Epub 2009 Aug 27. PMID: 19713490; PMCID: PMC2897713.