THE NATURE and SCOPE OF PSYCHOLOGY LESSON AIM Define psychology and explain basic theoretic approaches Despite their interest in the subject, students of psychology often find it difficult to answer this basic question in a clear, concise an d specific manner.
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.
The result is that females will have two copies of the sex-linked gene while males will only have one copy of this gene. If the gene is recessive, then males only need one such recessive gene to have a sex-linked trait rather than the customary two recessive genes for traits that are not sex-linked.