The key difference between sex-linked and autosomal is that sex-linked inheritance occurs via the genes located on sex chromosomes (X and Y chromosomes) while autosomal inheritance occurs via the genes located on autosomes.
Sex-linked and autosomal are the two basic inheritance modes that describe the mechanisms of transmission of any genetic character from generation to generation. These two inheritance modes follow Mendelian laws. These laws describe the inheritance of characters from parent to offspring using three basic principles: dominance, segregation, and independent assortment.
CONTENTS
1. Overview and Key Difference
2. What is Sex-linked
3. What is Autosomal
4. Similarities Between Sex-linked and Autosomal
5. Side by Side Comparison – Sex-linked vs Autosomal in Tabular Form
6. Summary
What is Sex-linked Inheritance?
As its name implies, sex-linked inheritance occurs via the sex chromosome of either X or Y. Therefore, sex-linked characters of off-springs depend on the sex chromosome (X and Y) transmitted from the parents. The Y chromosome has few genes while X chromosome has more genes. Hence, in offsprings, Y chromosomes express few traits while X chromosomes express more traits. Therefore, sex-linked inheritance is also referred to as X-linked inheritance.
Figure 01: Sex-linked Inheritance
Since females have a pair of X chromosomes, a female can be homozygous or heterozygous for sex-linked genes. Sex-linked inheritance occurs in two modes: sex-linked dominant and sex-linked recessive inheritance.
What is Autosomal Inheritance?
Autosomal inheritance is the transmission of traits present on a particular locus of an autosomal chromosome pair. Non-sex determining chromosomes are responsible for this inheritance. Moreover, their control takes place via the genes located on the autosomes. In autosomal inheritance, both males and females are affected with equal frequency.
Figure 02: Autosomal Inheritance
There are two types of autosomal inheritance: autosomal dominant and autosomal recessive inheritance. In autosomal dominant inheritance, the expression of traits are in heterozygote state and have a 50% probability of transmission of a particular trait to an offspring. In autosomal recessive inheritance, the trait is expressed only when the homozygous condition exists, and both parents must carry the recessive alleles in order to express it. Likewise, the autosomal inheritance causes most hereditary disorders that occur among the people.
What are the Similarities Between Sex-linked and Autosomal?
- Sex-linked and autosomal inheritance are two modes of inheritance that explain the transmission of characters from parent to offspring.
- Both occur via genes.
- These two inheritance modes follow Mendelian laws.
What is the Difference Between Sex-linked and Autosomal?
Sex-linked inheritance is due to the transmission of sex genes in X and Y chromosomes. Whereas, autosomal inheritance is due to the transmission of genes in autosomes or non-sex determining chromosomes. So, this is the key difference between sex-linked and autosomal. Unlike sex-linked inheritance, autosomal inheritance affects males and females with equal frequencies. Therefore, we can consider this too as a difference between sex-linked and autosomal.
Moreover, a further difference between sex-linked and autosomal is the types of each inheritance. There are two types of sex-linked inheritance as sex-linked recessive and sex-linked dominant inheritance while there are two types of autosomal inheritance as autosomal recessive and autosomal dominant inheritance. Also, unlike autosomal inheritance, you can easily understand the mode of sex-linked inheritance with the help of a family tree.
Summary – Sex-linked vs Autosomal
Sex-linked inheritance and autosomal inheritance are two types of inheritance patterns. Sex-linked inheritance occurs via the genes located in the sex chromosomes. Whereas, autosomal inheritance occurs via the genes in autosomes. Both types of inheritance exist as two types: recessive and dominant. However, autosomal inheritance occurs in equal frequency in males and females while it affects males and females differently in sex-linked inheritance. However, studying sex-linked inheritance is easy than studying autosomal inheritance. Thus, this summarizes the difference between sex-linked and autosomal.
Reference:
1. “X-Linked Inheritance.” Khan Academy, Available here.
2. “Human Genetics.” Wikipedia, Wikimedia Foundation, 10 Apr. 2019, Available here.
Image Courtesy:
1. “X dominant affected father” By GYassineMrabetTalk✉This W3C-unspecified vector image was created with Inkscape. – Own work based on source NLM illustration (Public Domain) via Commons Wikimedia
2. “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
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