BIOLOGY 1A03 Chapter Notes -Haemophilia, Y Chromosome, Chromosome

• School: McMaster University
• Department: Biology
• Course: BIOLOGY 1A03
• Professor: Lovaye Kajiura

Document Summary

Genes that are found on the sex chromosomes are called sex-linked genes. These genes can be on the x chromosome or on the y chromosome. If a gene is located on the y chromosome, it is a y-linked gene. These genes are only inherited by males because, in most instances, males have a genotype of (xy). Females do not have the y sex chromosome. Genes that are found on the x chromosome are called x-linked genes. These genes can be inherited by both males and females. Since genes for a trait may have two forms or alleles, one allele is usually dominant and the other is recessive. Dominant traits mask recessive traits in that the recessive trait is not expressed in thephenotype. In x-linked recessive traits, the phenotype is expressed in males because they only contain one x chromosome. The phenotype may be masked in females if the second x chromosome contains a normal gene for that same trait.