In this video, we're going to begin our lesson on autosomal inheritance. And so what's important to know is that a specific family trait or disorder can be tracked over multiple generations to identify the inheritance pattern. Now moving forward in our course, we're going to talk about two main types of inheritance patterns. And so the inheritance patterns can either be autosomal, or the inheritance pattern can be sex-linked. Now moving forward, we're first going to talk about autosomal inheritance and autosomal disorders, but then later in our course, in different videos, we'll talk more about the sex-linked disorders and sex-linked inheritance. But in our next video, we'll talk more about these autosomal disorders and inheritance. So I'll see you all there.
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Autosomal Inheritance - Online Tutor, Practice Problems & Exam Prep
Autosomal inheritance involves tracking traits or disorders through generations, categorized as autosomal dominant or autosomal recessive. Autosomal dominant disorders require only one dominant allele for expression, appearing in every generation, while autosomal recessive disorders necessitate two recessive alleles, often skipping generations. For example, polydactyly is an autosomal dominant disorder, whereas cystic fibrosis is autosomal recessive. Understanding these patterns is crucial for predicting inheritance and assessing genetic risks in families.
Autosomal Inheritance
Video transcript
Autosomal Disorders
Video transcript
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.
If a genetic counselor was examining a pedigree chart and noticed an occurrence of a disease in every generation, the counselor would most likely assume that the disease was caused by:
The pedigree chart shown depicts the inheritance pattern of __________.
Determine the likely pattern of inheritance in the following pedigree. List the genotypes of the numbered individuals in this order: #1, #2, and #3.
The following pedigree is for the ABO blood type group, which is an example of autosomal inheritance. Using the IA, IB, i for the alleles, fill in the top half of each box/circle with the genotype. Also, fill in the bottom half of each box/circle with the phenotype (A, B, AB, or O blood type). If it is impossible to know for certain a specific allele in the genotype, then place a '?' as a placeholder to represent the allele that is in question.
Problem Transcript
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What is autosomal inheritance and how does it differ from sex-linked inheritance?
Autosomal inheritance refers to the transmission of traits or disorders through non-sex chromosomes, known as autosomes. Humans have 22 pairs of autosomes and one pair of sex chromosomes. Autosomal inheritance can be either dominant or recessive. In contrast, sex-linked inheritance involves genes located on the sex chromosomes (X and Y). Traits or disorders linked to the X chromosome are more common, as the Y chromosome carries fewer genes. In autosomal inheritance, both males and females are equally likely to inherit the trait, whereas in sex-linked inheritance, the pattern can differ between genders due to the presence of one or two X chromosomes.
What are the key differences between autosomal dominant and autosomal recessive disorders?
Autosomal dominant disorders require only one dominant allele for the trait or disorder to be expressed. This means that individuals with either a homozygous dominant (AA) or heterozygous (Aa) genotype will exhibit the disorder. These disorders typically appear in every generation. Examples include polydactyly. On the other hand, autosomal recessive disorders require two recessive alleles (aa) for the trait or disorder to be expressed. Individuals with a heterozygous genotype (Aa) are carriers but do not show symptoms. These disorders often skip generations. An example is cystic fibrosis.
How can pedigrees be used to distinguish between autosomal dominant and autosomal recessive disorders?
Pedigrees are family trees that track the inheritance of traits or disorders through generations. In autosomal dominant disorders, affected individuals appear in every generation, and at least one parent of an affected individual is also affected. In contrast, autosomal recessive disorders often skip generations, and affected individuals may have parents who are carriers but do not show symptoms. By analyzing the presence or absence of the disorder in each generation and the genotypes of family members, one can determine whether a disorder is autosomal dominant or recessive.
What are some examples of autosomal dominant and autosomal recessive disorders?
Examples of autosomal dominant disorders include polydactyly, where individuals have extra fingers or toes, and Huntington's disease, a neurodegenerative disorder. These disorders require only one dominant allele to be expressed. Examples of autosomal recessive disorders include cystic fibrosis, which affects the respiratory and digestive systems, and sickle cell anemia, which affects the shape of red blood cells. These disorders require two recessive alleles to be expressed, meaning both parents must be carriers or affected for the disorder to appear in their offspring.
Why do autosomal recessive disorders often skip generations?
Autosomal recessive disorders often skip generations because they require two recessive alleles (aa) for the disorder to be expressed. Individuals with only one recessive allele (Aa) are carriers and do not show symptoms. If two carriers have children, there is a 25% chance that their child will inherit both recessive alleles and express the disorder. However, if carriers do not have children with another carrier, the disorder may not appear in the next generation, leading to the appearance of skipping generations.