Question

The results in the data table are from a simulated F₁ dihybrid test cross. The hypothesis that the two genes are unlinked predicts that the offspring phenotypic ratio will be 1:1:1:1. Using this ratio, calculate the expected number of each phenotype out of the 900 total offspring, and enter the values in that data table.

Short answer

F₁test hybrid is obtained from the crossing made between the cosmos plants. The expected number of each phenotype, out of the 900 offspring, is 225.

Step-by-step solution

Genes and their inheritance

Gene is the basic genetic material found in every organism. There are two types of alleles present in it such as linked alleles and unlinked alleles. Linked alleles are present in the chromosomes at a closer distance within a gene, and unlinked alleles are found in the different chromosomes.

Calculation of the expected from the given conditions

The expected number of unlinked genes is calculated as follows:

Total offspring\( = 900\)

Offspring phenotypic ratio\( = 1:1:1:1\)

Since the ratio equals the four different offspring, the total value divided by four will give the final expected number.

Expected number\( = \frac{{total{\rm{ }}number}}{{no.{\rm{ }}of{\rm{ }}offsprings}} = \frac{{900}}{4} = 225\)

The expected number of each offspring is 225.

Tabulation with the expected number results

Offspring from test cross of AaBb(F1)* aabb	Purple stem/short petals(A-B-)	Green stem/short petals (aaB-)	Purple stem/long petals(A-bb)	Green stem/ long petals(aabb)
Expected ratio if the genes are unlinked	1	1	1	1
Expected number of offspring (of 900)	225	225	225	225
The observed number of offspring (of 900)	220	210	231	239