Sex-linked vs Autosomal
Sex-linked and autosomal are the two basic inheritance modes and describes the mechanisms of transmission of any genetic character from generation to generation. These two inheritance modes follow Mendelian laws. Mendelian laws were first discovered by Gregor Mendel. Under these laws, he described the inheritance using three basic principles; namely, Dominance, Segregation, and Independent assortment.
Sex-linked Inheritance
As the name implies, the sex-linked inheritance is determined by the sex chromosome of either X or Y. Therefore, sex-linked characters of off-springs depend on which sex chromosome of X and Y is transferred from the parents. Genes on Y chromosome express very few traits while most of the traits are expressed by the genes on X chromosome. Therefore, sex-linked inheritance is often referred to as X-linked inheritance. Since females have a pair of X chromosome, a female can be homozygous or heterozygous for sex-linked genes. Sex-linked inheritance is further divided into two modes, namely; sex-linked dominant and sex-linked recessive inheritance.
Autosomal Inheritance
Autosomal inheritance is the transmission of traits on a particular locus on an autosomal chromosome pair. Non- sex determining chromosomes are responsible for this inheritance and controlled by genes located on autosomes. Here, both males and females are affected with equal frequency by this mode. The two types of autosomal inheritance are autosomal dominant and autosomal recessive inheritance. In autosomal dominant inheritance, traits are expressed in heterozygote state and have 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. Most of the hereditary disorders are caused by this inheritance mode.
What is the difference between Sex-linked and Autosomal Inheritance?
• Sex-linked inheritance is due to the transmission of sex genes (X and Y chromosome), whereas autosomal inheritance is caused by autosomes or non-sex determining chromosomes.
• Unlike the sex-linked inheritance, males and females are affected with equal frequencies by autosomal inheritance.
• Two types of sex-linked inheritance are sex-linked recessive and sex-linked dominant inheritance while the two types of autosomal inheritance are autosomal recessive and autosomal dominant inheritance.
• Unlike the autosomal inheritance, the mode of sex-linked inheritance is easily understood with the help of a family tree.
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