Question

Consider the trait, body color in the flour beetle, Tribolium castaneum, to be controlled by a pair of genes exhibiting complete dominance. The pair of contrasting alleles are \(\mathrm{E}\) for red body which is dominant to e for ebony body color. In a cross between a red-bodied female and an ebony-bodied male, 32 progeny are recovered, of which 18 are red-bodied and 14 are ebony- bodied. What are the genotypes of the parents and progeny?

Short answer

The genotypes of the parents and progeny in the given cross are as follows: the red-bodied female has a genotype of \(\mathrm{Ee}\), the ebony-bodied male has a genotype of 'ee', the red-bodied progeny have a genotype of \(\mathrm{Ee}\), and the ebony-bodied progeny have a genotype of 'ee'.

Step-by-step solution

We know that body color in flour beetles is determined by a pair of genes exhibiting complete dominance with the alleles \(\mathrm{E}\) representing red body color (dominant) and 'e' representing ebony body color (recessive). We have a cross between a red-bodied female and an ebony-bodied male, and the progeny are 18 red-bodied and 14 ebony-bodied. #Step 2: Determine the possible genotypes for the parents#

Since red body color is dominant and the female is red-bodied, her genotype can be either \(\mathrm{EE}\) or \(\mathrm{Ee}\). The male is ebony-bodied which is recessive, so his genotype must be 'ee'. #Step 3: Deduce the cross that most likely produced the given progeny#

Due to the ratio of red and ebony progeny, and the male's genotype being 'ee', it is more likely that the female's genotype is \(\mathrm{Ee}\). Therefore, the cross is between a heterozygous red-bodied female (\(\mathrm{Ee}\)) and an ebony-bodied male ('ee'). #Step 4: Use Punnett square to determine the possible genotypes of the progeny#

Set up a Punnett square with the female's genotype (\(\mathrm{Ee}\)) on one side and the male's genotype (ee) on the other. ``` | E | e | --------- e| Ee| ee| --------- e| Ee| ee| ``` #Step 5: Analyze the Punnett square to determine the genotypes of the progeny#

From the Punnett square, we can determine the probabilities of each genotype in the progeny: - \(\mathrm{Ee}\) (heterozygous red-bodied): 50% - 'ee' (ebony-bodied): 50% In the given progeny of 32, around half would be expected to be red-bodied (\(\mathrm{Ee}\)) and the other half ebony-bodied ('ee'). This is consistent with the observed progeny (18 red-bodied and 14 ebony-bodied), indicating that our assumption of the parents' genotypes is most likely correct. #Step 6: Conclusion - Determine the genotypes of the parents and progeny#

Based on the analysis above, the genotypes of the parents and progeny are: - Red-bodied female: \(\mathrm{Ee}\) - Ebony-bodied male: 'ee' - Red-bodied progeny: \(\mathrm{Ee}\) - Ebony-bodied progeny: 'ee'

Key concepts

Complete Dominance

Complete dominance is a fundamental principle in Mendelian genetics, where one allele completely masks the effect of another allele at a particular gene locus. This leads to only the dominant trait being expressed in the organism when a heterozygous genotype is present. In the case of complete dominance, the dominant allele will overshadow any influence from the recessive allele. For example:

• The dominant allele is represented by uppercase letters, such as \(\mathrm{E}\), which signifies the red body color in flour beetles.
• The recessive allele is denoted by lowercase letters, such as \(e\), indicating the ebony body color.

In beetles, if an individual has the genotype \(\mathrm{Ee}\), the dominant red body color \(\mathrm{E}\) will manifest, hiding the effect of the recessive \(e\) allele. Conversely, only when both alleles are recessive. \(ee\), will the ebony body color be expressed.

Genetic Cross

Exploring genetic crosses is crucial to understanding Mendelian inheritance patterns. A genetic cross involves breeding individuals to analyze how traits and the associated alleles are transmitted across generations. By examining the offspring, we can deduce the genotypes and phenotypes of the parents.In our given exercise, the genetic cross involves a red-bodied female Tribolium castaneum beetle and an ebony-bodied male. To interpret the results of this cross, we must consider the genotypes. Steps:

• Since the female exhibits the dominant red body color, her genotype could be \(\mathrm{EE}\) or \(\mathrm{Ee}\).
• The male shows the recessive ebony body color, so his genotype is definitively \(ee\).

With this genetic cross, we analyze the progeny to infer the most probable parental genotypes. Based on the distribution of red and ebony offspring, we can ascertain that the likely cross was between \(\mathrm{Ee}\) and \(ee\). This results in a predictable combination of offspring genotypes.

Punnett Square

The Punnett square is a handy tool in genetics for visualizing all possible allele combinations in offspring from a genetic cross. By setting up a grid, we can arrange the alleles from each parent on two sides and predict the genotypes of potential progeny. It effectively demonstrates Mendelian inheritance patterns for traits controlled by single-gene loci. In this exercise:

• The red-bodied female is represented as \(\mathrm{Ee}\).
• The ebony-bodied male is represented as \(ee\).

Using the Punnett square, we combine these alleles, mapping the female's \(E\) and \(e\) across the top with the male's \(e\) and \(e\) down the side. The results are:

• 50% of the offspring will be \(\mathrm{Ee}\), showcasing the red body color.
• 50% will be \(ee\), exhibiting the ebony body color.

This predicted outcome aligns with the actual observed phenotypic ratio of the progeny, confirming the effectiveness of the Punnett square in predicting genetic outcomes.