The dorsal pigment pattern of frogs can be either 'leopa...

Question

The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard

Compare and contrast the results of the reciprocal crosses in the context of autosomal gene inheritance.

Accepted Answer

Welcome back, everyone. Let's look at our next question. It says, If you cross a red eyed, big, a little a Drosophila and a white eyed little, a little, a Drosophila and produce a total of 150 offspring. How many of them are white eyed? Well, here we'll be looking for how many will be showing the recessive phenotype. So we can use a pundit square to look at the ratio of our offspring. And we've just got a cross of one gene with two alleles. So we just need a simple four box, punnett square on the top. Here, we'll put our heterocyclic parent. So big guy, big a in the first square, little A in the second and on the left side are homesickness, recessive little A in one box, little in the other. So when we fill out our different boxes, our result is that half of our boxes, we have had six offspring, big a little a and half of our boxes, homesickness, recessive offspring, little a little A. So of course, are hetero ziggy's offspring will expect to have red eyes as that's the dominant trait and our homes, I guess, recessive offspring will expect to have white eyes showing that recessive phenotype. So since we know that one half of the offspring, we'll have white eyes, Then half of 150 will equal 75. When we look at our answer choices, we see that choice d is 75. So we'll select that as our answer. We can go ahead and eliminate for say 150. Choice B 50 and choice C 100. As not being correct, Um the white eyed offspring will be choice D 75. See you in the next video.

Key Concepts

Autosomal Inheritance

Reciprocal Crosses

Phenotypic Ratios

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