Answer:
Pedigree analysis is a form of genetic analysis where the geneticist makes a diagram that shows an individual with a characteristic studied and all his known relatives.
The pedigree indicates the presence or absence of this characteristic and if the variation in its expression is applicable.
Mendel's principles still apply.
Example:
P1 Aa x Aa
F1 ¼ AA
½ Aa
¼ aa
When geneticists are analyzing pedigree, they look for a certain characteristic pattern that will help them determine how the characteristic studied is inherited.
-Auto dominant
The characteristic is expressed in both sexes and no sex is more prone than the other.
Phenotype appears in all generations and each affected person has a parent who suffers from the disease
Person who does not show the phenotype will not transmit the condition to the children.
In families where one of the parents has the gene, there is a 50% chance that any of the children will inherit the condition.
Example autosomal dominant conditions:
Achondroplasia
Neurofibromatosis
Huntington's disease
-Automatic recessive
Both sexes are affected
Although the parents appear to be normal the condition appears in their children in a fraction ¼ (both heterozygous parents).
The characteristic is only expressed when the individual is homozygous recessive.
The probability is higher among consanguineous marriages.
-Linked to dominant x
If a woman is heterozygous (XAXa) for a certain characteristic, we will have that 50% of her sons and 50% of her daughters are expected to inherit the X chromosome that carries the allele of the characteristic studied.
If the woman is homozygous (XAXA) for two dominant alleles then all her progeny will inherit the allele and also express the characteristic.
If a man is hemizygote for a dominant X-linked, therefore all his daughters will express the characteristic while none of their sons will do so since they inherit the Y chromosome from the father.
Affected men with normal wives do not have affected men, but affected daughters.
More abundant in females than in 50% males.
Example: Rett syndrome
