possess a mixture of traits from both parents preformation ism remained a

Possess a mixture of traits from both parents

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possess a mixture of traits from both parents, preformation-ism remained a popular concept throughout much of theseventeenth and eighteenth centuries.Another early notion of heredity was blending inheri-tance,which proposed that offspring are a blend, or mixture,1According to the pangenesisconcept, genetic informationfrom different parts of the body…1According to the germ-plasmtheory, germ-line tissue inthe reproductive organs…3…where it is transferredto the gametes.2…travels to thereproductive organs…2…contains a complete setof genetic information…3…that is transferreddirectly to the gametes.(a)Pangenesis conceptSpermEggEggSpermZygoteZygote(b)Germ–plasm theory1.8Pangenesis, an early concept of inheritance, compared withthe modern germ-plasm theory.
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Introduction to Genetics 000In June 2000, scientists from theHuman Genome Project and CeleraGenomics stood at a podium withformer President Bill Clinton toannounce a stunning achievement—they had successfully constructed asequence of the entire huan genome.Soon this process of identifying andsequencing each and every humangene became characterized as"mapping the human genome". Aswith maps of the physical world, themap of the human genome provides apicture of locations, terrains, andstructures. But, like explorers,scientists must continue to decipherwhat each location on the map can tellus about diseases, human health, andbiology. The map accelerates thisprocess, as it allows researchers toidentify key structural dimensions ofthe gene they are exploring, andreminds them where they have beenand where they have yet to explore.What does the map of the humangenome depict? when researchersdiscuss the sequencing of the genome,they are describing the identificationof the patterns and order of the 3billion human DNA base pairs. Whilethis provides valuable informationabout overall structure and theevolution of humans in relation toother organisms, researchers reallywanted the key information encodedin just 2% of this enormous map—theinformation that makes most of theproteins that compose you and me.Comprised of DNA, genes are thebasic units of heredity; they hold all ofthe information required to make theproteins that regulate most lifefunctions, from digesting food tobattling diseases. Proteins stand as thelink between genes andpharmaceutical drug development,they show which genes are beingexpressed at any given moment, andprovide information about genefunction.Knowing our genes will lead togreater understanding and radicallyimproved treatment of many diseases.However, sequencing the entire humangenome, in conjunction withsequencing of various nonhumangenomes under the same project, hasraised fundamental questions aboutwhat it means to be human. After all,fruit flies possess about one-third thenumber of genes as humans, and anear of corn has approximately thesame number of genes as a human! Inaddition, the overall DNA sequence ofa chimpanzee is about 99% the sameas the human genome sequence. As
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