 Today, we will look into how we can display phenotypes, determine genotypes, and predict traits of future generations within a family using a tool known as pedigrees. Firstly, let's recap on alleles. Alleles are variations of the same gene. That is, they are found in the same spot on homologous chromosomes, but they encode for different traits. You have two alleles for most genes because you get one from your father, and one from your mother. Alleles can be dominant or recessive, where the dominant allele is expressed over the recessive one. So now we will get onto what a pedigree is. It is a diagram that shows the occurrence of phenotypes of a particular gene within a particular family. In this example on this slide, we see a family with three generations, four grandparents, four parents, and three grandchildren. Now you may be asking what some of these symbols mean. Well circles are biological females, and squares are biological males. When a shape is shaded, it means an individual is affected, meaning they show a trait phenotypically. When a shape is not shaded, the individual is not affected, and their phenotype does not display the trait. Sometimes graphs may use half shaded shapes to indicate that someone is heterozygous, but this isn't too common, as this is a representation of genotype, but the pedigrees we will look at today will all be based on phenotype. So let's have a look at an example question, and this question is asking us to determine the possible genotypes of each person within this pedigree, and the trait that is shown within this pedigree is autosomal recessive. So first, let's have a look at the individuals that display the recessive trait, so those that are shaded. In order for these individuals to display a recessive trait, they must be homozygous recessive. And that means that their genotypes are composed of two lowercase a's. Now let's have a look at the first generation, specifically at individual one and individual two. These parents don't display the trait as they are not shaded, however we can see that they have an affected child who has two allials as we've previously worked out. This means the parents must both have a recessive allial that they have passed on to their child, but they must also have a dominant allial as they do not show the recessive trait, therefore they must have the dominant allial and the recessive allial present, meaning that they are heterozygous. Now we can apply the same concept to the parents of the affected child in the third generation. These parents are not affected, but they have an affected child, meaning that they are heterozygous for the trait. Now let's have a look at these three individuals here, and it is quite difficult to work out their exact genotype because we do not actually have enough information to work it out completely. However, since they do not display the trait as they are not shaded, we know that they must have at least one dominant allial, therefore they are either homozygous dominant or heterozygous for the trait. So looking at this last individual in the third generation, we know that they must at least have one dominant allial as they do not display the trait. However, if we look at their father, he only has an ability to pass on a recessive allial for this trait, because he is homozygous recessive. This means the child must have a recessive allial and a dominant allial. And we can see our final result to the question here. In summary, today we learned that pedigrees are useful for four reasons. They display phenotypes of a particular gene. They help us to determine genotypes. They can help us predict traits of future generations, and they can help us work out the pattern of inheritance of a particular gene.