In Some Gene Families the Genes Are Clustered in Defined

In some gene families the genes are clustered in defined chromosomal regions as a result of ___1____ gene duplication. That often occurs as a result of misalignment of chromatids: over a limited chromosomal region, the DNA sequences are paired but out of register. Subsequent ___2_____ in the mispaired region can generate chromatids with two copies of a gene. Successive gene duplications results in a cluster of highly related genes. Not all the gene copies are functional: some acquire inactivating mutations to become a type of ____3_____ known as a _____4_____ ____3____. In other gene families there may be up to many hundreds of more members scattered across the genome. They often have large numbers of ____5____ ____3______ , also known as ____6_____ that arose by copying the RNA transcripts of a functional gene using a ____7____ _____8_____ to make cDNA copies that integrated into the genome at other locations but subsequently acquired deleterious mutations.