Using a Pedigree Mendel

Using a Pedigree
Mendel observed several generation of pea plants to see patterns in the inheritance of traits. A simple way to model inheritance is to use a pedigree. A pedigree is a family historythat shows how a trait is inherited over several generations. A healthcare worker may use a pedigree to help a family understand a genetic disorder. A genetic disorder is a disease or disorder thatcan be inherited. If a family has a history of genetic disorder, the parents may want to know if their children could inherit the disorder. Some parents are carriers. Carriers have alleles for adisorder but do not show symptoms. Carriers can pass the allele for the disorder to their offspring.
Sex-linked Gene
The sex chromosomes, X and Y, carry genes for many characters other than gender. Asex-linked gene is located on either an X or a Y chromosome, but most are located on the X chromosome. Because it is much shorter that the X chromosome, the Y chromosome holds fewer genes. Females usuallyhave two X chromosomes. A recessive allele on one of the X chromosome will often have a corresponding dominant allele on the others. Males on the other hand, usually have an X chromosome and the muchshorter Y chromosome. Because it has few genes, the shorter Y chromosome may lack an allele that corresponds to a recessive allele on the longer X chromosome. So the trait for the single recessiveallele will be expressed in the male. Traits that are not expressed equally in both sexes are commonly sex-linked traits. Colorblindness is an example of a sex-linked trait that is expressed more inmales than females.
Dominant of Recessive?
If a person has a trait that is autosomal and dominant and has even one dominant allele, he or she will show the trait. If a person has a recessive trait andonly one recessive allele, he or she will not show the trait but may pass it on.
Heterozygous or Homozygous?
If a person is either heterozygous or homozygous dominant for an autosomal gene, his or...