What Is Sex-linked Inheritance?

Sex-linked inheritance is a biological process which involves the transmission of traits or characters from parents to offspring. X and Y are two sex chromosomes that carry alleles at their gene loci. These traits that are being transferred from one generation to the next generation are present on autosomes or sex chromosomes, i.e., the X chromosome or the Y chromosome.

Sex-linked genes are located on the X chromosome result in X-linkage. Similarly, Y-linkage refers to the gene which is present on the Y chromosome. Since females are homogametic with XX chromosome and males have XY chromosome, the Y-linked traits are transmitted via males only.

There are certain diseases which are linked to the X chromosome but are recessive, where females act as a carrier if they have only one copy of defective genes, such as colour blindness, haemophilia, etc. Males are heterozygous; hence, they are more prone to get sex-linked disorders because only one defective copy of genes is sufficient to cause diseases.

Types of Sex-linked Inheritance

As described earlier, there are two types of sex-linked inheritance: X-linked and Y-linked inheritance.

X-linked Inheritance

The X chromosome is larger than the Y chromosome. Any disorder or trait that is transmitted from the X chromosome is termed an X-linked inheritance. X-linked inheritance can either be recessive or dominant.

X-linked Recessive Inheritance	X-linked Dominant Inheritance
This trait is more common in males as they contain only one X chromosome.	Both males and females are affected by this type of disorder.
Haemophilia A and haemophilia B are examples of X-linked recessive inheritance.	Examples of X-linked dominant inheritance include Incontinentia pigmenti.

Y-linked Inheritance

If the mutated gene is present in the Y chromosome, then this is referred to as Y-linked inheritance. Since the Y chromosome is present in males only, Y-linked disorders are passed from fathers to male offspring. Hypertrichosis (presence of long dark hair on the ears) is an example of Y-linked inheritance.

Characteristic of Sex-linked Inheritance

Males are more affected by sex-linked traits in comparison to females because they are heterozygous.
The female passes the X-linked inheritance to both son and daughter, as they are homozygous to the X chromosome and pass the X chromosome to both offspring.

Sex-linked Inheritance Disorders

Some common examples include:

Haemophilia – It is a recessive sex-linked disorder which is also termed Bleeder’s disease. It is the inability to clot the blood, which results in uncontrolled bleeding. Read our article on Haemophilia to know more about the disorder.

Colour blindness – Yet again, a recessive sex-linked inheritance where the affected person fails to identify blue, red and green colours. You can learn more about it in our article on colour blindness.

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Frequently Asked Questions

What is sex-linked inheritance?

Sex-linked inheritance is a biological process which involves the transmission of traits or characters from parents to the offspring through sex chromosomes. X and Y are two sex chromosomes that carry alleles at their gene loci. These traits that are being transferred from one generation to the next generation are carried out in either the X chromosome or the Y chromosome.

What is X-linked inheritance, and what are its types?

Any disorder or trait that is transmitted from the X chromosome is termed an X-linked inheritance. X-linked inheritance can either be recessive or dominant. They are of two types, recessive X-linked inheritance and dominant X-linked inheritance.

What are the characteristics of sex-linked inheritance?

Males are more affected by sex-linked traits in comparison to females because they are heterozygous. The female passes the X-linked inheritance to both son and daughter, as they are homozygous to the X chromosome and pass the X chromosome to both offspring.