Modern Heredity Part 1 Concept Review 2

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.