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can be different genotypes. II III IV 1 || 1 1 1 2 2 2 1 2 1 3 2 3 4 4 2 4 1 In this pedigree, you are able to see how the trait skips the generations, but is still presently shown at the end. *this pedigree is autosomal, see page for more info* 5 5 6 6 5 6 5 6 *this pedigree is sex-linked, go to page for more info* Determining Genotypes of Dominant Pedigrees when looking at pedigrees as a whole, you always want to look at the individuals parents, siblings, etc. Not only does this help you figure out their genotype, but it also allows a chance to find out if the pedigree is dominant or recessive. In dominant pedigrees, shaded squares/circles always mean the individual has the disease/trait allele, meaning their genotype is AA Chomozygous dominant) or Aa (heterozygous).. However, you are not always able to know someone's genotype based on their parents. would never For example, the pedigree under shows an example of how some individuals genotypes are undisclosed/unknown because you know for sure. However, you can always absolutely sure that empty shapes are homozygous recessive (aa). be I II III IV ? 2 2 3 a Those who have a blank shape will ALWAYS be considered aa (homozygous recessive) because they are unaffected, meaning their trait will not show. With dominant pedigrees, heterozygous individuals are still accounted as affected because the trait will still be shown/present. Individual III-2 has to be heterozygous because looking t his parents, one dominant and one recessive allele must be passed down to him. A a Aa aa a Aaaa Determining Genotypes of Recessive Pedigrees Recessive Pedigrees are vastly different than from dominant pedigrees because heterozygous (Aa) individuals show as carriers Chalf shaded shapes) on pedigrees. Recessive Pedigrees are known for "skipping" generations as well. I II III 1 1 1 O 2 2 3 2 3 Sometimes recessive pedigrees look like this -> This pedigree is essentially the same as a regular one, just without carriers being shown. HOWEVER, you are able to infer that parents of affected individuals (such as 111-2 and III-3) have carrier parents. OR, that some individuals are carriers because of their parents (such as IV-1 because one of their parents was affected). ■ ■ Half filled Filled in Empty I II III IV Recessive alleles don't necessarily "skip" generations; rather, they just don't show their phenotype or present themselves. KEY = aa Chomozygous recessive) = AA Chomozygous dominant) = Aa (heterozygous) O 2 3 1 2 2 3 3 4 ■ Autosomal or Sex-linked? Sex-linked traits are determined by genes that are carried on the sex chromosomes (sex-linked inheritance). Most times, they are carried on the "x" chromosome because everyone has an "X" chromosome. Sex-linked inherited traits on pedigrees will traditionally be shown with more of one gender being affected by the disease than the other. usually in questions, they will describe the pedigrees as x-linked (female) or Y-linked (male). Autosomal Pedigrees will usually have an even distribution among both females and males. An example here: 13 14 DO 15 16 9 17 10 XX = female In this example, the disease is more prominent in males. 18 XY= male 11 19 | =