What is the probability of obtaining a triply recessive individual from the parents shown in Problem 18.

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Identify the genotypes of the parents given in Problem 18. Typically, this involves determining the alleles each parent carries for the three genes in question.

Determine the possible gametes each parent can produce by considering all combinations of alleles for the three genes. Use the principle of independent assortment if the genes are unlinked.

Calculate the probability that each parent contributes the recessive allele for each gene. For example, if a parent is heterozygous (Aa), the probability of passing the recessive allele (a) is 1/2; if homozygous recessive (aa), the probability is 1.

Multiply the probabilities for each gene from both parents to find the probability that the offspring is homozygous recessive (aa bb cc) for all three genes. This involves multiplying the probabilities of receiving recessive alleles from both parents for each gene.

Combine the probabilities for all three genes by multiplying them together to get the overall probability of obtaining a triply recessive individual.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mendelian Inheritance and Recessive Traits

Mendelian inheritance explains how traits are passed from parents to offspring through dominant and recessive alleles. A recessive trait is expressed only when an individual inherits two copies of the recessive allele. Understanding this helps determine the likelihood of offspring showing recessive phenotypes.

Probability in Genetics

Probability in genetics calculates the chance of inheriting specific allele combinations from parents. It involves multiplying the probabilities of independent events, such as inheriting recessive alleles from each gene, to find the overall likelihood of a particular genotype or phenotype.

Dihybrid and Trihybrid Crosses

Dihybrid and trihybrid crosses analyze inheritance patterns involving two or three genes, respectively. Each gene segregates independently, and the combined probability of recessive traits across multiple genes is found by multiplying individual gene probabilities, essential for determining triply recessive offspring.

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Trihybrid Cross

Related Practice

Textbook Question

In assessing data that fell into two phenotypic classes, a geneticist observed values of 250:150. She decided to perform a $χ$ ² analysis by using the following two different null hypotheses:

(a) the data fit a 3:1 ratio, and

(b) the data fit a 1:1 ratio.

Calculate the $χ$ ² values for each hypothesis. What can be concluded about each hypothesis?

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Textbook Question

The basis for rejecting any null hypothesis is arbitrary. The researcher can set more or less stringent standards by deciding to raise or lower the p value used to reject or not reject the hypothesis. In the case of the chi-square analysis of genetic crosses, would the use of a standard of p = 0.10 be more or less stringent about not rejecting the null hypothesis? Explain.

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Textbook Question

Consider the following pedigree.

Predict the mode of inheritance of the trait of interest and the most probable genotype of each individual. Assume that the alleles A and a control the expression.

Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.

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