Pedigree Analysis and Types of Inheritance Patterns

Pedigree Analysis

Introduction

Gregor Mendel first explained about the genetic traits which are passed from one generation to the next by experimenting with pea plants. Mendel developed three principles of inheritance which describe the transmission of genetic traits. In this lesson, we will learn about predicting genetic disorders in families using pedigree analysis.

Explanation

Mendel’s experiments proved that the ‘factors,’ what we all know as genes, are responsible the inheritance of traits.  Genes are the hereditary unit of organisms that are responsible for structural and functional changes in them. It’s also the reason for variation in organisms which might either result in a good or bad trait.
DNA sequences code for a specific protein. Any changes in this sequence, e.g., mistakes in amino acid sequence during DNA replication may cause a change within the genetic codes or chromosomal aberrations. This may be transferred from parents to offspring. Inheritance of genes may cause genetic disorders in the offspring.

An analysis represented by a pedigree chart with all the members of a family. They might have a disease or even carrier of the disease within the pedigree analysis

Symbols of Pedigree Analysis

Types of Inheritance Patterns

There are two types of inheritance patterns:

• Autosomal
• Sex-linked
• The individuals that have two copies of the same allele are called homozygous. 
• The individuals that have two copies of different alleles are called heterozygous. 
• The inheritance patterns depend on whether the allele is found as an autosomal chromosome or a sex chromosome.
• It also depends on whether the allele is dominant or recessive.

Autosomal Dominant

• The affected offspring has an affected parent.
• The affected parents can produce unaffected offspring.
• Occurs in every generation.

Autosomal Recessive

• Both parents of an affected offspring are carriers.
• Not seen in every generation.

X-linked Recessive

• Males are more frequently affected.
• Affected males are often present in each generation.

Pedigree Analysis for Polydactyl in Man

Polydactyl is the occurrence of extra fingers. Marriage between a polydactyl man and a non-polydactyl woman will produce three children one polydactyl daughter, one polydactyl son and a normal son.

Importance of Pedigree Analysis:

• Pedigree analysis is useful in medical research.
• This also helps in day-to-day counseling to parents about genetic traits.
• This chart helps families to identify the risk of inherited abnormalities or diseases among the offspring’s