Please explain patterns of sex linked genetic inhertitance and mention one or more examples of sex linked diseases

Some chromosomes not linked to sexual function are located on the sex chromosomes (X and Y). The Y chromosome is significantly shorter (50 million bp) than the X chromosome (153 million bp), thus the Y chromosome does not have many genes. This means that most sex-linked genetic conditions are X-linked. Because of the way in which sex chromosomes are inherited, their patterns differ from autosomal inheritance. Men are more likely to be affected by sex-linked conditions because they only have one X chromosome (XY) - they are always homozygous for the disease. Females have 2 (XX) so if they only have 1 diseased allele, they will be heterozygous and thus less affected by the condition. If they are heterozygous, they are called carriers and there is a 50:50 chance that they will pass the diseased allele on to their offspring. When looking at patterns of inheritance, there are things you must keep in mind: Only females can be carriers (heterozygous). Females cannot inherit a diseased allele of a recessive X-linked condition from an unaffected father. Affected females will always have affected sons - but their daughters will be carriers if the father is unaffected. Haemophilia and red-green colour blindness are the two most common sex-linked conditions.