Chapter 14 Notes
What is a pedigree?
A chart that shows relationships within a family that is used to show inheritance of traits.
∑ Square indicates male.
∑ Circle indicates female.
∑ Shaded square or circle indicates the individual expresses the trait.
∑ Unshaded square or circle indicates the individual does not express the trait or has the normal phenotype.
∑ Ĺ shaded square or circle indicates a carrier (heterozygous) individual.
∑ Horizontal line connecting circle to square indicates a marriage.
∑ Vertical line with a bracket connecting circles or squares to a marriage line indicates siblings (oldest child first)
∑ Roman numerals or capital letters indicate generations.
In humans, cystic fibrous is an autosomal trait. Normal mucus formation is dominant to cystic fibrous.
In humans, cystic fibrous is caused be a recessive allele (ff) that causes over production of mucus in the lungs and digestive tract. Suppose you are male #5 in generation III of the pedigree below. You have just married a young lady (#6) and she tells you that her mother had cystic fibrous. You are now afraid that your children will inherit this awful disease so you have a pedigree of your family done.
anytime parents donít have a trait but the child(ren) does, the parents are carriers (heterozygous).
anytime one of the parents has a trait but the child(ren) doesnít, the child is carrier
NOTE: This is an autosomal trait because the males and females are affected equally.
In humans, hemophilia is a sex-linked trait. Normal blood clotting is dominant to hemophilia.
HINT: the child has it but the parent doesnít, the parent is a carrier (heterozygous).
NOTE: If a female has 3 or more SONS that do not have a sex-linked trait, she is very likely homozygous dominant.
NOTE: This is a sex-linked trait because more males are affected than females.