Answer to Question #99446 in Genetics for Sara X Casey

Question

Discuss how crossing-over leads to greater variability of phenotypes. Give an example to help explain your answer.

Answer 1

Crossing-over provides the exchange of DNA sequences between homologous chromosomes during meiosis. The process causes the formation of a new arrangement of the genetic information stored in maternal and paternal chromosomes. As a result, due to new gene combinations present on the same chromosome, the genetic diversity of the offspring increases, making them different from parents. For example, let assume that one chromosome contains two mutated genes affecting the certain trait of the organism. Without crossing over, both mutated genes will be inherited by the offspring. However, the process of crossing-over can separate the genes between two homologous chromosomes. As only one homologous chromosome is inherited from one parent, the probability of inheritance for both mutated genes decreases, and the offspring will possess only one mutated gene.