In this video, we're going to focus on autosomal disorders. And so traits or disorders that are associated with autosomes, which recall from our previous lesson videos are non-sex chromosomes, can be inherited in 2 ways that we have numbered down below, number 1 and number 2. And so the first way that these autosomal traits or disorders can be inherited is as autosomal dominant disorders. Now autosomal dominant disorders, as their name implies, are going to be disorders associated with autosomes in which individuals with at least one dominant allele will have the disorder. And so for example, the individual could either be homozygous dominant or heterozygous and still have the disorder because they have at least one dominant allele. Now dominant disorders tend to appear in every generation without skipping a generation. Now, the second way that autosomal disorders can be inherited is as autosomal recessive disorders. Of course, as their name implies, autosomal recessive disorders are disorders associated with autosomes in which the individuals that are homozygous recessive are going to be the ones that display the disorder. And so only individuals that have 2 lowercase letters for their genotype, or 2 alleles, will actually have the autosomal recessive disorder, which is different than having at least one capital, or one dominant allele, to have the disorder. Now autosomal recessive disorders, they tend to skip a generation. And so, if we take a look at our image down below, we can further distinguish between autosomal dominant disorders and autosomal recessive disorders pedigrees.
Over here on the left what we have is an autosomal dominant disorder. A disorder that's known as polydactyly which results in having extra digits, either extra fingers or extra toes. And so, because it is an autosomal dominant disorder that means that it's associated with the dominant allele. And so what you can see here is that having a capital F would result in having extra fingers or toes, or about polydactyly, whereas having the lowercase f would be having the normal number of fingers and toes. And so individuals that have at least one capital F are going to have polydactyly since it is an autosomal dominant disorder. And so notice that all of the ones that are shaded with the blue background are ones that are affected or that actually have polydactyly. And notice that all of them have at least one capital F, which is going to give them polydactyly. And all of the individuals that are not affected are going to be homozygous recessive and have 2 lowercase f's, and so the ones that are not affected are again not shaded.
Now over here on the right-hand side, what we're showing you is an autosomal recessive disorder, which is specifically cystic fibrosis. And so because cystic fibrosis is an autosomal recessive disorder, it's actually associated with the lowercase allele, the recessive allele, instead of being associated with the dominant allele. And so, individuals that have a dominant allele are going to be saved from having the disorder. They're gonna be healthy individuals. Whereas individuals that have 2 lowercase a's, individuals that are homozygous recessive, are going to actually have cystic fibrosis. And so that's exactly what we see over here in this pedigree. All of the shaded individuals are individuals that have the disorder, cystic fibrosis, and notice that all of them are homozygous recessive. And so, all of the ones that are not affected have at least one dominant allele to save them from having the disorder. Now one thing to note is that autosomal recessive disorders tend to skip an entire generation. And so notice that this generation here in the middle is not being affected, and the disorder seems to skip an entire generation. Whereas with autosomal dominant disorders, it tends to be present in every generation. And so this here concludes our introduction to autosomal disorders and distinguishing between autosomal dominant disorders and autosomal recessive disorders. And we'll be able to get some practice applying these concepts as we move forward in our course, so I'll see you all in our next video.