Autosomal dominant
It is the most common type of inheritance
This shows up in every generation, they do not skip generations (vertical inheritance)
It is transmitted from father to son
There is usually an equal number of affected males and females
So, if you look at the pedigree, and you see a lot of squares and circles that are completely shaded or half shaded, and there is one in every generation, then it is autosomal dominant.
Autosomal Recessive
The disease appears in the children of unaffected parents. This means that both parents do not phenotypically express the disease, but their children do. This is because the parents are carries of the disease. They must be heterozygous for their children to have the disease. The disease can skip generations pheontypically.
The affected kids are both males and females.
There are not a lot of shaded circles or squares, meaning that there are not a lot of affected people in the pedigree.
Sex linked
In sex linked, only males are affected,
however father to son transmission is NOT observed. Females can be affected, but for that to occur they would need a mother who is a carrier of the disease and a father who has the disease. The reason father to son transmission is not seen is because the father donates his Y chromosome to his son (the only way the child could be male) and thus cannot donate the X chromosome carrying the disease. Only the mother who either has the disease or is a carrier for the disease can donate an X chromosome with the disease on it. The reason why sex linked disease occurs in males is because females have 2 X chromosomes (yes one does get deactivated into a polar body), so they would need a recessive disease on both X chromosomes to express the disease. Whereas in males the Y chromosome is much smaller than the X chromosome and is made of heterochromatin (its pretty much useless except for the SRY gene) so if a male's X chromosome that he got from his mother has a recessive gene, there is no other gene that is dominant to it that prevents its expression. A common mistake I used to make while doing Punnett squares was to put the recessive gene for the male w/ the disease on his Y chromosome, but remember, his mother gave him the gene, and the gene is on his X chromosome.
It is always a good rule of thumb that if you are trying to figure out someone's genotype or phenotype on the pedigree to look at their parents, and their parent's parents to determine what genotype the person is exactly.
Another random tidbit is that only mutations gametes (eggs and sperm) are inherited.
You may also get a pedigree analysis with blood types and paternity testing( I did in my genetics class).
