17.6 Sex linkage

Question 1

what are sex linked genes

Answer 1

any gene that carries an X or Y chromosome

Question 2

the issue with recessive alleles on the X chromosome

Answer 2

• y chromosomes are smaller than x chromosomes
• recessive genes on the X chromosome may not have an equivalent on the Y chromosome
• this means that if a male inherits a recessive disorder form they mother via the X chromosomes there will become a sufferer as there is not equivalent on their Y chromosome to mask it

Question 3

sex link in haemophilia

Answer 3

• mainly affects males as they dont have a second X chromosome to mask the faulty allele
• females must inherit a faulty allele firm both their mother and father
• always inherited from the mother in males due to her X chromosome
• affected sons can only pass it on to their daughters from his X chromosome