In Drosophila, gray body color is dominant to ebony body color, w...

Question

In Drosophila, gray body color is dominant to ebony body color, while long wings are dominant to vestigial wings. Assuming that the P₁ individuals are homozygous, work the following crosses through the F₂ generation, and determine the genotypic and phenotypic ratios for each generation.

gray, long x gray, vestigial

Accepted Answer

Hi everyone. Let's look at our next question. It says a tall pea plant with purple flowers which is big B. Little B. Big C. Little C. Is crossed with another tall P. Plant with purple flowers of the same genotype, what is the probability of producing short and purple flower offspring? So let's note we have a di hybrid cross here since both parents have the same genotype. And in that case it's big B. Little B. Big C. Little C. And we see that that gives the phenotype of tall and purple. So since both are hetero sickness, we know that tall and purple must be both the dominant traits here. So it's asking us what's the probability of producing short and purple flower offspring? So for offspring are short with purple flowers? Well, we know that purple is the dominant tree but the short is the recessive trait. So we have offspring that are recessive in one trait and dominant in the other. Well, we know that in a di hybrid cross we can recall that the fanatic ratio of the offspring is 9-3-3-1. nine being dominant in both traits. One being recessive in both traits and three and 3 being dominant in one And recessive in one. So we know that since our offspring were looking for something that we recessive uh for shortness but dominant for purple, that we're looking for three. There are 16 possibilities total for offspring. So we're looking at a ratio of choice d. Three out of 16 being short and purple. So if you want to look at the punnett square for this, go ahead and put that up. Here we go. So we've got our two hetero parents with their identical combination of gametes and we want something that's short. So recessive which is the B. Allele. So we're looking for little B. Little B. So we know that that's going to be anywhere that we get little B. From both parents. So we've got that here. But this fourth one here inherits the recessive little B. But it's also got recessive little C. And we're looking for the ones that show the purple dominant trait. So that's not going to include this box here which is recessive in both traits. So here are three squares where the offspring inherit that recessive trait for shortness but still show the dominant purple trait. So that correctly shows that our ratio is choice D. Three out of 16th is the probability of producing short purple offspring. See in the next video

Key Concepts

Mendelian Genetics

Genotypic and Phenotypic Ratios

Homozygosity and Heterozygosity

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