Difference Between Autosomal and X-linked

Main Difference – Autosomal vs X-linked

Autosomal and X-linked are two types of inheritance patterns that describe the inheritance of a particular genetic trait from one generation to the next. The main difference between autosomal and X-linked is that autosomal inheritance is the inheritance of traits that are determined by the genes in the autosome whereas X-linked inheritance is the inheritance of traits determined by the genes in one of the sex chromosomes. Generally, genes come in pairs, each inherited from one parent. Alleles are the variant forms of genes. The dominant alleles prevail over the recessive alleles.

Key Areas Covered

1. What is Autosomal Inheritance
     – Definition, Types, Examples
2. What is X-linked Inheritance
     – Definition, Types, Examples
3. What are the Similarities Between Autosomal and X-linked Inheritance
     – Outline of Common Features
4. What is the Difference Between Autosomal and X-linked Inheritance
     – Comparison of Key Differences

Key Terms: Autosomal Inheritance, Autosomal Dominant Inheritance, Autosomal Recessive Inheritance, Inheritance Patterns, Mutation, Single-Gene Disorders, X-linked Inheritance, X-linked Dominant Inheritance, X-linked Recessive Inheritance

What is Autosomal Inheritance

Autosomal inheritance refers to a pattern of inheritance in which the transmission of traits depends on the genes in the autosome. The two types of autosomal inheritance are autosomal dominant and autosomal recessive.

Autosomal Dominant Inheritance

The presence of a single copy of a mutated gene or the inheritance of a diseased allele from an affected parent is sufficient for a particular individual to be affected by the autosomal dominant traits. Since the autosomal dominant traits are inherited from parents to the offspring, the autosomal inheritance is also called vertical inheritance. Both male and female offspring have an equal probability of inheriting autosomal dominant traits. Male-to-male transmission can also be observed in autosomal dominant inheritance since a single mutated allele is sufficient for the expression of the trait. Huntington disease, Marfan syndrome, and myotonic muscular dystrophy are examples of autosomal dominant inheritance. The autosomal dominant inheritance is shown in figure 1.

Figure 1: Autosomal Dominant Inheritance

Autosomal Recessive Inheritance

Both copies of genes are mutated in autosomal recessive inheritance. Each mutated gene can be inherited from a parent who serves as the carrier for the trait. Cystic fibrosis and sickle cell anemia are two examples of autosomal recessive inheritance.

What is X-linked Inheritance

 X-linked inheritance refers to a pattern of inheritance in which the transmission of traits depends on the genes in the sex chromosomes. The two types of X-linked inheritance are X-linked dominant inheritance and X-linked recessive inheritance.

X-linked Recessive Inheritance

Mutation in the genes of the X chromosome causes the X-linked recessive disorders. Females have two X chromosomes while males have X and Y chromosomes. In females, both X chromosomes should have the mutation in order to be affected by the disease. In males, the mutation should occur on their X chromosome. Since the possibility of the occurrence of two mutated alleles in females is less, most females are not affected by the disease. However, most males are affected by the disease as they have a single X chromosome. But, male-to-male transmission of the disease cannot be identified in X-linked recessive inheritance. Hemophilia, color blindness, and Fabry disease are examples of X-linked recessive inheritance. The X-linked recessive inheritance is shown in figure 2.

Figure 2: X-linked Recessive Inheritance

X-linked Dominant Inheritance

Mutation in one of the sex chromosomes causes X-linked dominant inheritance. In X-linked dominant inheritance, a mutation in a single chromosome is sufficient for the individual to be affected by the disease. In most  X-linked dominant disorders, males show severe symptoms. No male-to-male transmission can be observed in X-linked dominant inheritance. Fragile X- syndrome is an example of X-linked dominant inheritance.

Similarities Between Autosomal and X-linked Inheritance

• Autosomal and X-linked inheritance are two types of inheritance patterns.
• Both autosomal and X-linked inheritance are composed of dominant and recessive stages of inheritance.
• Both autosomal and X-linked inheritance are associated with various single-gene disorders.

Difference Between Autosomal and X-linked Inheritance

Definition

Autosomal: Autosomal inheritance is a pattern of inheritance in which the transmission of traits depends on the genes in the autosome.

X-linked: X-linked inheritance is a pattern of inheritance in which the transmission of traits depends on the genes in the sex chromosomes.

Types of Genes

Autosomal: Autosomal inheritance describes the inheritance patterns of the genes in the autosome.

X-linked: X-linked inheritance describes the inheritance patterns of the genes in one of the sex chromosomes.

Type of Inheritance

Autosomal: Autosomal inheritance exhibits Mendelian inheritance patterns.

X-linked: X-linked inheritance exhibits criss-cross inheritance.

Contribution of Alleles

Autosomal: Both alleles of a particular gene are involved in controlling the autosomal trait.

X-linked: The alleles in the X chromosome are often involved in the determination of the X-linked trait.

Influence on the Sex

Autosomal: Autosomal traits equally affect both sexes.

X-linked: X-linked traits often affect male individuals.

Types

Autosomal: Autosomal dominant and autosomal recessive are the two types of autosomal inheritance.

X-linked: X-linked dominant and X-linked recessive are the two types of autosomal inheritance.

Male-to-male Transmission

Autosomal: Male-to-male transmission is observed in autosomal dominant inheritance.

X-linked: Male-to-male transmission is not observed in X-linked dominant inheritance.

Complexity

Autosomal: Autosomal inheritance is somewhat difficult to understand within generations.

X-linked: X-linked inheritance is easy to understand within generations.

Examples

Autosomal: Widow’s peak and Hitchhiker’s thumb are autosomal traits.

X-linked: Hemophilia, and color blindness are X-linked traits.

Conclusion

Autosomal and X-linked are two types of inheritance patterns that describe the inheritance of genes over generations. Autosomal inheritance describes the inheritance of the genes in the autosome. X-lined inheritance describes the genes in one of the sex chromosomes. Therefore, the main difference between autosomal and X-linked is the type of genes involved in these two types of inheritance patterns.

Reference:

1. “What are the different ways in which a genetic condition can be inherited? – Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, Available here.

Image Courtesy:

1. “Autosomal dominant – en” By Domaina – Own work based on File:ABO system codominance.svg and File:Autodominant.jpg (CC BY-SA 3.0) via Commons Wikimedia
2. “2928 X-linked Recessive Inheritance-new” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia