Concept explainers
a) To begin your analysis, state your null hypothesis.
b) Perform a chi-square analysis. Make sure to analyze your traits to be consistent with the information provided. Clearly present your results in a table as shown in the attachement called Testing Genetics Ratios (Hint: should the traits be tested in males and females?)
c) State the correct # of degrees of freedom, calculate the chi-square value and show the approximate p value.
d) Make a statement of how the p value relates to whether you decided to reject or not reject, your null hypothesis.
e) Finally, make a concluding statement about your original genetic hypothesis(es) based on chi-square analysis.
Fully typed, organized correctly, correct spelling, and grammar.
Genetic hypothesis for each allele:
Trait: Leg length
- Hypothesis: The wild-type and mutant alleles for leg length are incomplete dominant relative to each other.
Trait: Wing shape
- Hypothesis: There are two alleles for wing type, one dominant and one recessive. Truncated wings allele is recessive, and the gene is X-linked.
Leg Length:
For the leg length trait, we see that the number of individuals with the medium leg
Additionally, there are no specific differences or ratios mentioned between males and females for leg length, indicating that the mode of inheritance is autosomal and specific to each allele. This supports the hypothesis of autosomal inheritance, with incomplete dominance between the alleles.
- The data set shows three phenotypic categories for leg length: wild type (long leg), medium leg, and truncated wings.
- The ratio of wild type females (355) to wild type males (167) suggests an autosomal inheritance pattern since both sexes show the wild type phenotype.
- The presence of medium leg females (679) and medium leg males (351) supports the hypothesis of incomplete dominance. The heterozygous individuals (F1) exhibit the intermediate phenotype.
- The absence of purebred short-legged individuals suggests the dominance of the long leg allele over the short leg allele.
Wing Shape:
The data set for wing shape: wild type (short leg) and truncated wings. Notably, the truncated wings phenotype is observed only in males, and there are no categories for truncated females. This absence of truncated females strongly suggests an X-linked inheritance pattern.
To further support this hypothesis, we can calculate the numbers provided in the data set. As mentioned in the example, by adding up the counts for truncated males (337 + 165 + 168), we obtain a total of 670 truncated individuals. However, since there are no categories or counts for truncated females, we can conclude that the number of truncated females is zero.
- The data set includes two phenotypic categories for wing shape: wild type (long leg) and truncated wings.
- The presence of truncated wings only in males indicates an X-linked inheritance pattern.
- The absence of truncated wings in females supports the hypothesis that the allele for truncated wings is recessive to the wild type allele.
- The presence of truncated wings in some males (e.g., truncated wings, medium leg male: 337) suggests that these males inherited the recessive allele from their mother (X-linked).
Explanation:
This discrepancy in the occurrence of the truncated wings phenotype between males and females provides strong evidence for an X-linked recessive inheritance pattern. Since males have only one X chromosome, the presence of a single truncated wing allele (X^T) is sufficient to manifest the phenotype, while females would require two copies of the allele.
Genetic symbols for the alleles:
Leg Length:
- Wild-type (short leg) allele: L+
- Medium leg allele: LM
- Long leg allele: LL
Wing Shape:
- Wild-type allele: W
- Truncated wing allele: w
Explanation:
- The expected phenotypic ratio in the F2 generation for leg length will be 1:2:1, with 25% wildtype (short leg), 50% medium leg, and 25% long leg individuals.
- The expected phenotypic ratio in the F2 generation for wing shape will be 50% wildtype female, 25% wildtype male and 25% truncated male (only males will show this phenotype).
Ratios:
- Females
- Legs: (short/wildtype: medium: long) – 1: 2: 1
- Wings: (wildtype: truncated) – 2: 0
- Males
- Legs: (short/wildtype: medium: long) – 1: 2: 1
- Wings: (wildtype: truncated) – 1: 1
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