Final answer:
Classical genetics methods like linkage analysis allowed early geneticists to deduce gene function by observing mutated phenotypes before the era of recombinant DNA technology. Reverse genetics enables modern researchers to start with DNA sequences and discover their roles by observing resulting phenotypes or by gene alteration.
Step-by-step explanation:
Before the advent of recombinant DNA technology, most genes were identified through the study of phenotypes resulting from gene mutations. Classical genetics methods, including linkage analysis, relied on observing mutated phenotypes to infer the function of specific genes. For instance, traits like flower color and pollen shape in pea plants exhibited physical linkage due to their proximity on the same chromosome, as discovered by early geneticists following Mendel's work on genetics.
Linkage analysis helped in creating the first genetic maps, allowing the study of genes that showed independent assortment or were linked by being located close to each other on chromosomes. With modern techniques such as reverse genetics, the approach is reversed, starting with a known DNA sequence and investigating the resultant phenotype, or altering a gene to understand its function better. This way, gene function can be characterized by mutation or deletion, similar to how the function of a body part is understood by its loss.
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