Figure 13.3 Inheritance patterns of unlinked and linked genes are shown. In (a), two genes are located on
different chromosomes so independent assortment occurs during meiosis. The offspring have an equal chance
of being the parental type (inheriting the same combination of traits as the parents) or a nonparental type
(inheriting a different combination of traits than the parents). In (b), two genes are very close together on the
same chromosome so that no crossing over occurs between them. The genes are therefore always inherited
together and all of the offspring are the parental type. In (c), two genes are far apart on the chromosome such that
crossing over occurs during every meiotic event. The recombination frequency will be the same as if the genes
were on separate chromosomes. (d) The actual recombination frequency of fruit fly wing length and body color
that Thomas Morgan observed in 1912 was 17 percent. A crossover frequency between 0 percent and 50 percent
indicates that the genes are on the same chromosome and crossover occurs some of the time.
