x linked recessive traits

• • Predominantly expressed in males, because males only carry one x chromosome
• • Females carrying an x-linked recessive allele might not express the trait as a second x chromosome could mask a recessive trait
• • This means female will be termed carrier (heterozygous genotype – the recessive allele may be passed onto her offspring)
• • X linked dominant traits will show different patterns
• If the red colour is dominant, the genotypes for a female are:

  • X^R X^R – red-eyed female
  • X^R X^r– red-eyed female (carrier)
  • X^r X^r – white-eyed female