In Drosophila, an X-linked recessive mutation, scalloped (sd), ca...

Question

In Drosophila, an X-linked recessive mutation, scalloped (sd), causes irregular wing margins. Diagram the F₁ and F₂ results if (a) a scalloped female is crossed with a normal male; (b) a scalloped male is crossed with a normal female. Compare these results with those that would be obtained if the scalloped gene were autosomal.

Accepted Answer

Hey everyone, Let's take a look at this question together. Which of the following best describes autism a recessive disorder characteristics. Let's recall what we've learned about autism a recessive disorder and try to figure out which of the following best describes those characteristics that we know that when we're talking about autism or recessive disorder, we know that it involves defects in both autism traits, defects in both copies of art is omo beans. And we also know that it's hugely only found in the offspring and not in the parents because those parents are actually carriers. So parents are carriers, meaning that they have that gene, but they do not express the gene. And so since it is a defect in both copies of the autism genes, if we have a defect in one copy, it leads to a dominant disorder. If it is expressed because only one copy would mean that it is dominant over that gene that does not have the disorder. And in the case of that dominant disorder, If one abnormal gene is inherited from the mother or father, the child will likely express the disorder. And so, knowing these characteristics of that autism or recessive disorder, let's take a look at our answer choices to figure out which of the following best describes it. Answer choice A says the trade can only be expressed by the zygote if it inherits two mutated alleles, we know that since we're dealing with that recessive disorder, the offspring has to get one copy of that mutated allele from both parents in order to express it. So the only way it can be expressed is if it inherits two mutated alleles, which means that answer choice A. Is a true statement. Let's go ahead and make a note. Answer choice B says the disease or trait must be present in both parents. Now we know that both parents are usually carriers and do not express that condition. So answer choice B. Is incorrect and because of that answer choice C. Is also incorrect because answer choice C. Says the disease or trait must be present in at least one parent, which is also not true. And lastly, answer choice D. Says the trade can only be expressed by the zygote if it inherits one mutated alil, which we know that a defect in one copy leads to a dominant disorder and not that autism or recessive disorder. So answer choice D. Is incorrect. And answer choice A. Is the only true statement listed here, so it is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

Key Concepts

X-linked Inheritance

Punnett Square

Autosomal vs. X-linked Genes

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