Explain why the inheritance of colour pattern in tortoise beetles is described as involving multiple alleles.
A tortoise beetle with dfm-b phenotype was crossed with another tortoise beetle showing dfm-b phenotype. Construct a genetic diagram to show the outcome of this cross, including the ratio of offspring phenotypes. Parental phenotypes: dfm-b $\times$ dfm-b. Parental genotypes: Gametes: Offspring genotypes: Offspring phenotypes: Ratio of offspring phenotypes:
The colour pattern phenotype involves alleles that show codominance. There is also a dominance order among the alleles (dominance hierarchy). Use the information in Table 3.1 to: • identify the codominant alleles; • list the dominance hierarchy with the alleles arranged from the most dominant to the least dominant.
Researchers carried out two crosses. Cross 1: female veraguensis tortoise beetles were crossed with male metallic tortoise beetles. The results are shown in Table 3.2. Cross 2: female veraguensis tortoise beetles were crossed with male veraguensis tortoise beetles. The results are shown in Table 3.3.
Using Table 3.1, work out the genotypes of each parental beetle used in cross 1 and cross 2. Cross 1: Cross 2:
An assumption was made that female tortoise beetles have XX chromosomes and males have XY chromosomes. Gene L is not located on the X chromosome. It was concluded that colour pattern phenotype follows autosomal inheritance. Explain how the evidence in Table 3.3 supports this conclusion.
Identify a statistical test that can be used to decide whether the observed phenotypic ratio differs significantly from the expected ratio.