how to analyse any trait by using pedigree analysis??
- A pedigree is used to determine mode of inheritance of a particular trait.
- Pedigree analysis is the analysis of inheritance of traits in several generations of a family.
- A particular trait under study is represented in a family tree.
- By using pedigree analysis, inheritance of a specific trait, abnormality or disease, can be traced.
- Here is a sample pedigree for you.
- Squares represent males
- Circles represent females.
- Horizontal lines connecting a male and female represent mating.
- Vertical lines extending downward from a couple represent their children.
- Subsequent generations are therefore written underneath the parental generations and the oldest individuals are found at the top of the pedigree.
There are about 200 hereditary traits identified in human beings.
Some of them are:
- Skin colour – Normal (Dominant) Albino ( Recessive)
- Hair - dark, curly (Dominant) Light, straight( Recessive)
- Colour vision – Normal ( dominant) Colour blind ( Recessive)
- Eyes – Brown , large ( Dominant) Blue , small ( Recessive)
More to know:
- The inheritance of sex-linked disorders differ in males and females while in case of autosomal disorders, there is no distinction in males and females.
- Here are some examples of sex-linked and autosomal disorders.
- When the disease is sex linked, it is inherited differently in males and females because of the difference in their sex chromosomes. You might be knowing that females possess two X chromosomes while males possess an X and a Y chromosome
A trait is said to be dominant when it is expressed even in the heterozygous condition, i.e it will be expressed even when the individual carries only one copy of the gene coding for the particular trait. But for a recessive trait to express itself, it has to be in the homozygous condition,i.e there should be two copies of the gene coding for the particular trait.
Here is the pedigree chart of an autosomal dominant trait
Here is the pedigree chart of an autosomal recessive trait