The key difference between autosomal and X-linked pedigree is that autosomal pedigree describes the inheritance of traits of the genes in autosomes, while X-linked pedigree describes the inheritance of traits of the genes in sex chromosomes.
A pedigree graphically represents the presence or absence of a trait with reference to the relationship among parents, offspring, and siblings. Therefore, pedigrees help in analyzing the inheritance pattern of a particular trait throughout the family. It is important to determine whether the trait is dominant or recessive and to determine if the pedigree chart shows an autosomal or X-linked trait before analyzing the pedigree.
CONTENTS
1. Overview and Key Difference
2. What is Autosomal Pedigree
3. What is X-Linked Pedigree
4. Similarities – Autosomal and X-Linked Pedigree
5. Autosomal vs X-Linked Pedigree in Tabular Form
6. Summary – Autosomal vs X-Linked Pedigree
What is Autosomal Pedigree?
An autosomal pedigree is a graphical representation of the pattern of inheritance of a particular trait that affects both males and females in equal proportions, which are present in the autosomes. These chromosomes are also called somatic chromosomes. Autosomal pedigrees follow Mendelian inheritance patterns. Here, the graphical representation of family members and relationships is interpreted through standardized symbols. The significance of autosomal pedigree is that it shows the effect of a particular trait in equal proportions on both males and females. Hence, both males and females get affected with a ratio of 50:50.
Figure 01: Autosomal Pedigree
Autosomal traits can be either autosomal dominant or autosomal recessive. Therefore, autosomal pedigree can represent autosomal dominant analysis and autosomal recessive analysis. Autosomal dominant pedigrees relate facts about the traits that do not undergo any skipping of generations, while autosomal recessive pedigrees show the pattern of generation-skipping of traits. Autosomal recessive pedigrees are often seen in consanguine marriages, where the recessive characteristics are passed to the next generation. Cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are some conditions that can be analyzed using autosomal pedigrees.
What is X-Linked Pedigree?
X-linked pedigree is a graphical representation of a pattern in the inheritance of a particular trait that is sex-linked and more commonly affect either males or females. X-linked pedigree follows the criss-cross type inheritance pattern. X-linked pedigree is of two types: dominant and recessive. Therefore, X-linked pedigree represents both X-linked dominant, and X-linked recessive traits analyses.
Figure 02: X Linked Pedigree
In X-linked dominant pedigrees, the traits have an increased effect on females than males. Moreover, traits do not skip generations. Furthermore, an affected son should have an affected mother, while an affected daughter could have either an affected mother or father. In X-linked recessive pedigree, the traits have an increased effect on males. Traits may skip generations, and an affected son could have an unaffected mother. Duchenne muscular dystrophy, some types of colorblindness, and hemophilia A are examples of traits that can be analyzed by an X-linked pedigree.
What are the Similarities Between Autosomal and X-Linked Pedigree?
- Autosomal and X-linked pedigrees are graphical representations of inherited traits throughout a family.
- They use standard symbols for representation.
- Moreover, they analyze both dominant and recessive traits.
- Both show the presence or absence of a trait.
- Determination of genotypes can take place using both pedigree analyses.
- Determination of phenotypes can take place using both pedigree analyses.
What is the Difference Between Autosomal and X-Linked Pedigree?
Autosomal pedigree describes the inheritance of traits of the genes in autosomes, while X-linked pedigree describes the inheritance of traits of the genes in sex chromosomes. Thus, this is the key difference between autosomal and X-linked pedigree. The autosomal pedigree shows a Mendelian inheritance pattern while the X-linked pedigree shows criss-cross inheritance. Moreover, male-to-male transmission is observed in autosomal pedigree and is not observed in X-linked pedigree.
The below infographic presents the differences between autosomal and X-linked pedigree in tabular form for side-by-side comparison.
Summary – Autosomal vs X-Linked Pedigree
A pedigree graphically illustrates the presence or absence of a trait with reference to the relationship among parents, offspring, and siblings. It uses standardized symbols. Autosomal pedigree and X-linked pedigree are the two main types of pedigrees. Autosomal pedigree describes the inheritance of traits of the genes in autosomes, while X-linked pedigree describes the inheritance traits of the genes in sex chromosomes. With regards to the pattern of inheritance, autosomal pedigree shows a Mendelian inheritance pattern, and X-linked pedigree shows Criss-cross inheritance. So, this summarizes the difference between autosomal and X-linked pedigree. Using both pedigrees, it is possible to determine genotypes and identify the phenotypes.
Reference:
1. “Pedigree Analysis.” Carnegie Mellon University.
2. “Pedigrees Review (Article) | Heredity.” Khan Academy.
Image Courtesy:
1. “Autosomal Dominant Pedigree Chart” By Jerome Walker – Own work (CC BY 2.5) via Commons Wikimedia
2. “Sex linked inheritance” By Simon Caulton – Own work (CC BY-SA 3.0) via Commons Wikimedia
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