shown are the F2 results of two Mendel's monohybrid crosses. Mendel crossed 2 heterozygote parents. If he were to expect segregation to happen normally, do the results match his expectations? state a null hypothesis that you will test using chi-square analysis. Calculate the chi-square value and determine the p value for both crossesa. Full pods: 882; constricted pods: 299 (full pods are dominant over constricted)b. violet flowers: 705; white flowers: 500 (violet dominant over white)

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Asked Sep 19, 2019
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shown are the F2 results of two Mendel's monohybrid crosses. Mendel crossed 2 heterozygote parents. If he were to expect segregation to happen normally, do the results match his expectations? state a null hypothesis that you will test using chi-square analysis. Calculate the chi-square value and determine the p value for both crosses

a. Full pods: 882; constricted pods: 299 (full pods are dominant over constricted)

b. violet flowers: 705; white flowers: 500 (violet dominant over white)

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Expert Answer

Step 1

A genetic cross is breeding of two genetically compatible organisms to study their inheritance pattern.  In a single genetic cross, a single trait or multiple traits can be observed. Monohybrid cross is the one in which only one trait is observed in a cross between two homozygous (both the alleles of the gene are same) individuals. During the cross, the alleles are transferred to the offspring according to some laws. When the alleles of a gene segregate independently without affecting the segregation of other, then this law is called law of segregation. In a cross, the first generation of the parents is known as the F1 generation. The F1 generation self-cross to give rise to their next generation which is known as the F2 generation.

When individuals of a population cross in nature, there may occur some deviations from the idle case. To check the probability of population crossing against the law, null hypothesis is proposed. A chi-square test is done to check whether the proposed null hypothesis is accepted or rejected using the expected and observed number of individuals of a phenotype.

Step 2

a) In the given case, the said population crossed under law of segregation and following results were observed:

Full Pods: 882

Constricted pods: 299

Where, full pods are dominant (the allele will express even in the presence of other allele) over constricted pods.

So, the total population of F2 generation comes out to be: 1,181

According to the law of segregation, the expected phenotypic ratio of the population should be 3:1 which means that 75% of population should possess dominant phenotype while only 25% of population should possess recessive phenotype.

Here, according to total population and standard phenotypic ratio, expected number of full pods should be around 886 and number constricted pods should be around 295.

Now, since there is difference between the observed and expected values, we propose the null hypothesis that the two variables are not associated.

Step 3

To accept or reject the null hypothesis, chi-square test will be done to find the value o...

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where xChi square fo Observed value fe = Expected value

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