 Next, we're going to talk about the different types of inheritance with genetic populations. First and foremost, you have autosomal dominant. Autosomal dominant is seen across many generations. You see both male and females are affected with this. This is on the autosome, not a sex chromosome, so that it does not have any effect to the male or female population. To be able to diagnose this, you need to get a good family history. You'll see approximately half of the offspring from a heterozygous individual will be affected. The heterozygous individual is going to have one copy of the mutated gene and one copy of a regular gene. That mutated gene, since it is dominant, will be expressed in every offspring that it is present in. You see over here on the right, this mutated A is present in both of those two offspring, and then when there is not a mutated A, you have a homozygous normal offspring. Looking below in the chart, you'll see that the affected individual is highlighted in gray, so the male here is affected, and he passes it off to approximately half of his offspring. He has five offspring, there are three affected individuals that pass it off. Those three individuals will then pass it off to approximately half of their offspring. You see this female here passes it off to a male and a female. The next female that was affected did not have any offspring, and then the following male that was affected passed it off to another male and another female over here. Examples of this disease or this inheritance trait is achondroplasia, autosomal dominant polycystic kidney disease. You'll see it in familial adenomatous polyposis. Osther Weber-Rindow syndrome, Huntington's disease, Marfan's syndrome, men, neurofibromatosis type 1, which is also known as von Recklinghausen's disease, neurofibromatosis type 2, and the von Hippel-Lindow disease. I will note we mentioned Huntington's disease as a autosomal dominant mode of inheritance, and that also shows anticipation that we talked about earlier, so it can have more than just one trait to it. Next we're going to talk about autosomal recessive. Autosomal recessive is a trait that has only shown up in the phenotype when both genes are present. So you've got to have two carrier parents that are heterozygous to be expressed in the offspring. So someone that carries a recessive trait will not express that recessive trait unless both genes are recessive, or both alleles are recessive. So unaffected individuals have two-thirds chance of being a carrier from a heterozygous parent. Examples of this is autosomal recessive polycystic kidney disease. It's right there in the name. Autosomal recessive fibrosis, Friedrich's ataxia, glycogen storage diseases, hemochromatosis, cartaginous syndrome, all of the mucopolysaccharidosis except for Hunter's syndrome, phenylketonuria, sickle cell anemia, thalassemias, and Wilson's disease. Looking over here at the chart on the right, you'll see both of the parents here are carriers, they're heterozygous for the trait, and they will pass it off to three of their offspring. One will be normal, and then two will be heterozygous, and then you'll have one that's affected here. So this exact example is seen down here. Both of these parents here are heterozygous carriers, and they pass it off to a small amount or one fourth approximately of their offspring, which is this one individual. Now there's a couple of things here to look at. So over here, this person that was affected had an autosomal recessive trait, came in and was married into this person, and they had children, and you see they have two people that were affected that doesn't seem to follow what we just mentioned. What you're seeing is someone that is homozygous recessive with someone that is heterozygous, so you're having three different genes passed off here, so there's a higher likelihood of offspring being affected. Furthermore, this one offspring that was affected married another person that was affected. All of their offspring now are going to be affected because it is a autosomal recessive homozygous, autosomal recessive homozygous. They have no normal traits, therefore all of their offspring will be affected. Moving on now to the X-linked recessive. With X-linked recessive, one of the biggest things to note is that there will not be any male-to-male transmission of this gene. The heterozygous mother will pass it off to 50% of her sons because she passes off 1X to a son and the male passes off 1Y. So over here on the chart you'll see this 1X that will be passed from a mother and passed down she will have a carrier female and an affected male. Most often X-linked recessive is only going to be seen in males. There are times it is seen in females but that means that the father has to be affected and the mother would have to be a carrier. It does skip generations often. So looking down here at the graph you see that no one in the parent section is affected. They did have two offspring that are affected both males here and here. The male here was not affected, did not pass it off. This male did not pass it off into a offspring but you will see some of these offspring will be carriers. Furthermore you do see that there are some generational skips here in offspring that were not affected but then they had children that were affected down here. Both are males that are affected. This is seen in Bruton's egg amoglobulinemia, Dachane and Becker's muscular dystrophy, Fabry's disease, G6PD deficiency, hemophilia A and B, Hunter syndrome, Leish-Nein syndrome, ocular albinism, Ornithine transcarbomylase deficiency and Wiskott-Aldrich's syndrome. All of those are excellent recessive. Moving on to X-linked dominant. This is seen in every person that carries the trait. It is a dominant trait. Affected mothers will transmit this to 50% of their sons and daughters. It is not expressed in sons more than daughters because it is a dominant trait. Affected fathers will transmit it to all of his daughters and will not transmit it to his sons because he does not pass that X gene over to the son. He only passes the Y. You see this in Fragile X syndrome, Alport syndrome and hypophosphatemic rickets. Specifically, hypophosphatemic rickets, a little note there, that is where you have loss of phosphate at the proximal tubule and just a little tidbit there. Let's look over here at the Punnett square. You'll see that the X in this example is from the mother. The mother passes it off to one of her females and one of her males. The other two are left unaffected. Down here below on the graph, we have an effective male passing it off only to his daughters. The daughter will then pass it off to half sons, half daughters, which you see down here in the third generation. And there is no other transmission to other successive generations because this is dominant. It will be seen. Moving along, finally we come to mitochondrial inheritance. Mitochondrial DNA is transmitted from the mother and the mother only. All children that have an affected mother will show signs of this disease. If a father has this disease, he will not pass it on to his children at all because mitochondrial DNA only comes from the mother. There is a potential list to be subject to variable expressivity, so remember that. An example of mitochondrial inheritance is Milos syndrome. Milos stands for mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. We're seeing lactic acidosis secondary to a failure of oxidative phosphorylation here. The muscle biopsy often will show a red ragged fiber, and that's due to the accumulation of disease mitochondria in the subsarcolema of the muscle fiber. Another example is the Lieber Hereditary Optic Neuropathy. What this is is cell death in the optic nerve neurons, and it causes a subacute bilateral vision loss, commonly seen in teens and young adults. Mostly it's 90% males, and it's usually a permanent disease. Looking over the chart here on the right, you can see the mother is affected, and she passes it on to all of her offspring. The female on the left here also passes it off to all of her offspring as well, as it's a mitochondrial inheritance. These two males, however, do not pass it off to any of their offspring, as the males do not pass off mitochondrial DNA to any of their offspring.