The following table shows the results of different matings...

The following table shows the results of different matings between jimsonweed plants that had either purple or white flowers and spiny or smooth pods. Determine the dominant allele for the two traits and indicate the genotypes of the parents for each of the crosses. $$\begin{array}{ccccc} & \text { Parents } & & {}{} {\text { Offspring }} \\ \hline & \begin{array}{c} \text { Purple } \\ \text { Spiny } \end{array} & \begin{array}{c} \text { White } \\ \text { Spiny } \end{array} & \begin{array}{c} \text { Purple } \\ \text { Smooth } \end{array} & \begin{array}{c} \text { White } \\ \text { Smooth } \end{array} \\ \hline \text { a. purple spiny } \times \text { purple spiny } & 94 & 32 & 28 & 11 \\ \text { b. purple spiny } \times \text { purple smooth } & 40 & 0 & 38 & 0 \\ \text { c. purple spiny } \times \text { white spiny } & 34 & 30 & 0 & 0 \\ \text { d. purple spiny } \times \text { white spiny } & 89 & 92 & 31 & 27 \\ \text { e. purple smooth } \times \text { purple smooth } & 0 & 0 & 36 & 11 \\ \text { f. white spiny } \times \text { white spiny } & 0 & 45 & 0 & 16 \end{array}$$

The following table shows the results of different matings between jimsonweed plants that had either purple or white flowers and spiny or smooth pods. Determine the dominant allele for the two traits and indicate the genotypes of the parents for each of the crosses.
$$\begin{array}{ccccc}
& \text { Parents } & & {}{} {\text { Offspring }} \\
\hline & \begin{array}{c}
\text { Purple } \\
\text { Spiny }
\end{array} & \begin{array}{c}
\text { White } \\
\text { Spiny }
\end{array} & \begin{array}{c}
\text { Purple } \\
\text { Smooth }
\end{array} & \begin{array}{c}
\text { White } \\
\text { Smooth }
\end{array} \\
\hline \text { a. purple spiny } \times \text { purple spiny } & 94 & 32 & 28 & 11 \\
\text { b. purple spiny } \times \text { purple smooth } & 40 & 0 & 38 & 0 \\
\text { c. purple spiny } \times \text { white spiny } & 34 & 30 & 0 & 0 \\
\text { d. purple spiny } \times \text { white spiny } & 89 & 92 & 31 & 27 \\
\text { e. purple smooth } \times \text { purple smooth } & 0 & 0 & 36 & 11 \\
\text { f. white spiny } \times \text { white spiny } & 0 & 45 & 0 & 16
\end{array}$$

Key Concepts

Segregation and Independent Assortment

Segregation is the principle that each parent contributes one allele for a gene to their offspring, and independent assortment means that the distribution of alleles for one trait is unaffected by the distribution of alleles for another trait. These two principles are fundamental in analyzing multiple traits simultaneously and in predicting the ratios of various phenotypes observed in genetic crosses.

Genotype and Phenotype

Genotype refers to the underlying genetic makeup of an organism, specifically the alleles present at a gene locus, while phenotype is the observable physical expression of those genes. Understanding the relationship between genotype and phenotype is essential when determining the genetic composition of the parents from the observed offspring.

Punnett Squares and Crosses

Punnett squares provide a systematic way to predict the genotype and phenotype ratios of offspring resulting from a particular cross. They are especially useful in dihybrid or single trait crosses for visualizing how dominant and recessive alleles combine during fertilization.

Mendelian Inheritance

This concept refers to the set of principles related to the transmission of genetic traits from parents to offspring as first described by Gregor Mendel. In such inheritance patterns, traits are determined by discrete units (genes) that exist in different forms (alleles), and predictable ratios in offspring can be obtained based on the combination of parental alleles.

Dominant Allele

A dominant allele is one that expresses its trait in the phenotype even when only one copy is present in an individual's genotype. Identifying which allele is dominant within a trait enables predictions about how the trait will appear in the offspring when crossed with individuals with different genotypes.

Transcript

00:01 In order to answer this question, let's talk about inheritance.

00:03 You have a table here.

00:05 This is the table, okay? and it says the following table shows the results of different meetings between genesomeweed plants that had either purple or white flowers and spiny or smooth paths.

00:16 Let remind the dominant allele for the two traits and indicate the genotypes of the parents for each of the crosses.

00:23 So you're having here many crosses.

00:25 Okay.

00:25 And in order to make it easy, to make this question easy, remember that when you have a dihybrid cross because in this case you have two jeans.

00:33 You have the color and also you have the pot shape.

00:40 So you have two traits in this case, two genes.

00:43 Okay, so when you perform this cross, it means when both parents are heterocycles for both genes, you're going to have a phenotypic weight of 9 -3 -3 -1.

00:56 Okay? you have a total of 16 here because 9 plus 3 plus 3 plus 1 is equal to 16.

01:02 So 9 16s i want to be for this phenotype.

01:06 316s are going to be for this phenotype, 316s for this phenotype, and 116s for this phenotype.

01:14 So here you have apparently all of the possibilities for these crosses.

01:18 So one of them, one of these cross should be heterocygot for both genes for both pines.

01:24 And as you can see here, you have to get a 9, 3, 3 ,000.

01:28 3 -1 ratio.

01:30 So in this case, what are the two possible crosses here that can be, that can have this phenotypic ratio? this one not because you have zero and zero and you don't have any zero here.

01:43 Also this one, we're not going to use this, this or this.

01:47 We're going to use this one here and this one here.

01:50 Okay, and let's see which of them can fit for this phenotypic ratio.

01:55 First, let's go for this one here, okay? so you have a a total of 89 plus 92 plus 31 plus 27.

02:07 This is equal to 239.

02:10 So in order to find a frequency, you have to divide each of these numbers by the total.

02:15 And let's see if you get frequency similar to this one here.

02:18 Again, in this case, you have 916s.

02:21 916 is equal to 0 .05625.

02:29 In this case, you have 3 .6.

02:31 6th, 3 divided by 16, this is equal to 0 .1875.

02:39 Also here you have 0 .1875.