Situs inversus is a congenital condition in which the ma...

Question

Situs inversus is a congenital condition in which the major visceral organs are reversed from their normal positions. Investigations into the genetics of this abnormality revealed that individuals with at least one dominant allele (SI) of an autosomal gene are normal but, surprisingly, of individuals that are homozygous for a recessive allele (si), 1/2 are situs inversus and 1/2 are normal.

What genotypes and phenotypes are expected in progeny from a cross of two si si individuals?

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. What is the probability that a child born to parents who are carriers for an autosomal recessive disorder will also be a carrier. The answer options are A zero B one out of four, C, one out of two and D, three out of four. For this problem. Let's use the letter A to represent our lists. The disorder is autosomal recessive, meaning affected individuals will have a homozygous recessive genotype. The question states that the parents are carriers. So they have a recessive a little but are not affected by the disorder, meaning both parents are heterozygous. So we are solving for the probability that a child will be a carrier or in other words, the probability that the F one offspring will also have a heterozygous genotype to determine the offspring genotype, we can use a punt square to do a cross between two heterozygous parents on the screen is the punt square results of that cross. The genotypes of the offspring are one homozygous dominant, two heterozygous and one homozygous recessive. Therefore, two out of four offspring are carriers or have the heterozygous genotype. That means if we reduce that down, we have one out of two our carriers. So the correct answer is option C one out of two. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

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