Final answer:
Genes in close proximity on the same chromosome are likely to be inherited together due to linkage; the frequency of crossing-over determines how far apart genes are, allowing geneticists to create linkage maps. This phenomenon alters typical Mendelian inheritance predictions such as the expected 9:3:3:1 ratio in a dihybrid cross.
Step-by-step explanation:
When two genes are located in close proximity on the same chromosome, they are likely to be transmitted through meiosis together. This is known as linkage. For example, in a dihybrid cross involving traits like flower color and plant height, if tall and red alleles are on one chromosome and short and yellow alleles on the other, gametes will typically carry these combinations together.
Thus, in the absence of crossing-over, you would expect only the parental combinations of traits to be present in the offspring. However, as the distance between two genes increases, the probability of crossing-over events occurring between them also increases, leading to a higher chance of the genes being inherited independently.
Geneticists can use the frequency of such recombination events to construct linkage maps, helping them determine the location of genes on chromosomes and understand genetic disorders and inheritance patterns in humans and other organisms.
If genes are on different chromosomes, they undergo independent assortment and have a 50 percent chance of being separated during meiosis. When genes are closer than 50 percent crossover frequency on the same chromosome, they tend to be inherited together, which is a sign of linkage. Low crossover frequency indicates that genes are physically close on the chromosome and are less likely to recombine.