Question

Please explain a genetic pedigree to diagnose: recessive disorder, dominant disorder, x-linked disorder(recessive and dominant) or mitochondrial disorder.

Answer 1

Answer : The pedigree chart generally displays a family chart where it we can easily find the members of the family who are genetically affected by a genetic trait.

They can be used to simplify and detect mode of transmission and often used to study the genetics of inherited diseases. For example, pedigrees can be analyzed to determine the mode of transmission of various genetic diseases like Hemophilia. In pedigree analysis, we need to look for any clues that will allow us to decide if the trait which are present are dominant or recessive or whether it is linked to an autosomal chromosome, or to a X chroomsome.

Dominant traits

Recessive traits

Pedigree of x-linked dominant disorder

In this condition, The affected males pass the condition on to all their daughters but to none of their sons

while the females married to unaffected males pass the condition on to half their sons and daughters.

Pedigree of X-linked recessive disorder

In this condition, a female showing the phenotype can show some result only from a mating if both the mother and the father bears the allele.while,  a male with the phenotype can be produced only when the mother itself carries the allele. The offspring of the affected male are also affected, but all his daughters must be carriers because females must also receive one of their X chromosomes from their fathers too and Half the sons who are born to these carrier daughters are affected as well. for example , Hemophilia.

It is important to remember that an unaffected individual can never have any alleles of a dominant trait and the unaffected individual can be a carrier with one allele of a recessive trait where if the trait is X-linked, a single recessive allele is more than enough for a male to be affected.

A father always transmits his allele of X-linked genes further to his daughter, but not his sons. While a mother transmits an allele of X-linked genes to both of her daughters and her sons.