Pedigrees: Study with Video Lessons, Practice Problems & Examples

A pedigree is a family tree chart used to track phenotypes across generations, with circles representing females and squares for males. Shaded shapes indicate affected individuals. Relationships are depicted through horizontal lines for mating pairs and vertical lines for offspring connections. Reading pedigrees involves identifying generations, such as P (parental), F1 (first generation), and F2 (second generation). Understanding these relationships helps in analyzing inheritance patterns and genetic traits, essential for studies in genetics and heredity.

Pedigrees

In this video, we're going to introduce pedigrees. A pedigree is a chart or family tree that depicts family relationships, and pedigrees can be used to track a phenotype over many generations. Within a pedigree, circles represent females, whereas squares represent males. Shaded or colored shapes represent affected individuals that have the phenotype of interest. Horizontal lines that go from side to side connect mating parents, whereas vertical lines that go up and down are used to connect parents to offspring. If we take a look at our example below, we can get a better feel for these symbols and connections on a pedigree. Notice that circles that are not shaded represent unaffected females, whereas squares that are unshaded represent unaffected males. The shaded-in circles and squares represent affected females and affected males, respectively. When we say affected, we mean that they have whatever phenotype is of interest. Horizontal lines connecting two shapes represent mating parents; this would be the mating male and the mating female. Below, the vertical connections you see will connect the parents to the offspring, who we have down below. Of course, if these offspring are connected like what we see here, that means that they are siblings coming from the same set of parents. As we move forward in our course, we'll be able to talk more about pedigrees and how to read them. But for now, this is our brief introduction to the symbols on a pedigree, and I'll see you all in our next video.

How to Read Pedigrees

In this video, we're going to talk a little bit more about how to read pedigrees. Pedigrees are typically read from the top to the bottom, starting from the first generation. Now in our example below, we're going to use this pedigree to determine the relationships between the indicated individuals on the pedigree. Over here, what we have are the indicated individuals. Here we're going to put the specific relationships. And again over here we have the pedigree itself. The first set of shapes that we see at the very top represents the very first generation or the P generation, if you will. You can see that we have an unaffected male because it's an unshaded square, mating with an affected female because it's a shaded circle. And then, of course, the next generation of organisms that we see here would be the F₁ generation, the first generation of children. And then, of course, the generation below them would represent the F₂ generation, the generation that is going to be the children of the F₁ generation.

What you'll notice here is that person number 1, indicated here with the number 1, is going to be person number 5's father. The reason for that is because there is a vertical connection between person 1 and person 5, and that means that person 5 is the offspring of person 1, and of course, person 1 is a male so that means that person 1 is going to be person 5's father. Moving on to the next one, we have person number 7, which is over here, and person number 4, which is over here. What you'll notice here is that both of them are vertically connected to the same sets of parents, which means that they are siblings to one another, and more specifically, because they're both females they are sisters. So person 7 and person 4 are sisters.

Lastly, we have person number 11, which is down here, and person 6 which is up here. It says person number 11 is person 6's daughter. The reason that we know that again is because there is a vertical connection between the two, so that means that these will be the parents and these will be the offspring. And of course, 11 is a circle which means that she is a female. So that means that she would be person 6's daughter. This here concludes our example problem, and we'll be able to get more practice reading pedigrees as we move along through our course. But for now, this here concludes this video, and I'll see you all in our next one.

Diagrams depicting family relationships and phenotypes for a genetic disorder are:

• A. Pedigree charts.
• B. Karyotypes.
• C. Punnett squares.
• D. Bell-shaped curves.

Here’s what students ask on this topic:

What is a pedigree in genetics?

A pedigree in genetics is a chart or family tree that depicts family relationships and is used to track phenotypes across multiple generations. In a pedigree, circles represent females and squares represent males. Shaded shapes indicate individuals who are affected by a particular phenotype or genetic trait. Horizontal lines connect mating pairs, while vertical lines connect parents to their offspring. Pedigrees are essential tools for analyzing inheritance patterns and understanding genetic traits, making them crucial in studies of genetics and heredity.

How do you read a pedigree chart?

Reading a pedigree chart involves identifying the symbols and lines that represent family relationships and phenotypes. Circles represent females, and squares represent males. Shaded shapes indicate affected individuals. Horizontal lines connect mating pairs, while vertical lines connect parents to their offspring. Pedigrees are read from top to bottom, starting with the first generation (P generation), followed by the first generation of children (F1 generation), and then the second generation of children (F2 generation). Understanding these symbols and connections helps in analyzing genetic inheritance patterns.

What do the symbols in a pedigree chart represent?

In a pedigree chart, different symbols represent various family members and their genetic status. Circles represent females, and squares represent males. Shaded or colored shapes indicate individuals who are affected by the phenotype or genetic trait of interest. Unshaded shapes represent unaffected individuals. Horizontal lines between shapes indicate mating pairs, while vertical lines connect parents to their offspring. These symbols and lines help in visualizing and analyzing genetic inheritance patterns across generations.

What is the significance of shaded shapes in a pedigree chart?

Shaded shapes in a pedigree chart are significant because they represent individuals who are affected by the phenotype or genetic trait being studied. These shaded shapes help in identifying patterns of inheritance and determining whether a trait is dominant, recessive, autosomal, or sex-linked. By analyzing the distribution of shaded shapes across generations, geneticists can make inferences about the mode of inheritance and the likelihood of the trait appearing in future generations.

How can pedigrees be used to track genetic disorders?

Pedigrees can be used to track genetic disorders by mapping the occurrence of a disorder across multiple generations within a family. By identifying affected individuals (shaded shapes) and their relationships to unaffected individuals (unshaded shapes), geneticists can determine the mode of inheritance (dominant, recessive, autosomal, or sex-linked). This information helps in predicting the risk of the disorder appearing in future generations and can guide genetic counseling and medical decision-making.