julia@slovax.UUCP (Julia Haviland) (11/15/86)
> Wrong. Flat wrong. *NO* new genotypes are created by sexual > reproduction, cross breeding or not. New phenotypes may possibly be, > but not likely. New genotypes are created *ONLY* by mutation. Your > analogy to a new book created out of words in the dictionary is totally > misleading. Who arranges the words/genes in your scenario? Sexual > reproduction is a random selection from the parents. A more accurate > analogy would be the random selection of half of the short stories from > each of two anthologies to form a new anthology. > Wayne Throop <the-known-world>!mcnc!rti-sel!dg_rtp!throopw Wayne seems to be confusing genotype with gene. A gene is loosely defined as the unit which produces some observable trait, behavior, or biochemical event. Genotype is the collection of all genes a particular organism has. Sexual reproduction usually involves each parent contributing 1/2 of the alleles for a particular gene to the offspring. Most of the parental genes will be the same, but a certain number will almost always be different. Sexual reproduction is random only in that which allele, of the two alleles of a gene an individual can have, goes to a particular gamete and which gametes unite to form offspring is random. For example one parent may contribute the allele for blood type "A" and the other for blood type "B". The child will be blood type "AB", a different genotype and phenotype than either parent. Each parent will contribute only one allele for each gene locus so that reproduction is not a random mixing of genes, but an ordered manner of allowing recombination of differing copies of the same gene (= allele). Given the number of possibly varying genes in most organisms, each act of sexual reproduction will probabilistically produce a new genotype. Some possibly lesser number of these new genotypes will produce a unique phenotype. Granted this is just reshuffling what already exists. However, genes do not act in isolation, but the phenotypic effect of genes may vary depending on other genes present. Note that in the population of a species, more than two alleles for a gene may exist but only two alleles can be present in any given individual. >Your > analogy to a new book created out of words in the dictionary is totally > misleading. Who arranges the words/genes in your scenario? Sexual > reproduction is a random selection from the parents. A more accurate > analogy would be the random selection of half of the short stories from > each of two anthologies to form a new anthology. > Wayne Throop <the-known-world>!mcnc!rti-sel!dg_rtp!throopw
throopw@dg_rtp.UUCP (Wayne Throop) (11/18/86)
> julia@slovax.UUCP (Julia Haviland) >> Wrong. Flat wrong. *NO* new genotypes are created by sexual >> reproduction, cross breeding or not. > Wayne seems to be confusing genotype with gene. A gene is loosely > defined as the unit which produces some observable trait, behavior, or > biochemical event. Genotype is the collection of all genes a > particular organism has. [...] Sexual reproduction is random > only in that which allele, of the two alleles of a gene an individual > can have, goes to a particular gamete and which gametes unite to form > offspring is random. Silly, sloppy me. Julia is completely correct. However, please don't let my blunder (and my subsequent overly smug assertion of Jan Wasilewsky's "ignorance" of biology) blunt the two main points I was trying to make. These are still valid. First, no new genetic material is created by sexual reproduction. New genotypes do not new genes make. Second, the selection of genetic material from parents to form offspring is random (within rules, as mentioned by Julia above). The analogy that Jan Wasilewsky raised (likening sexual reproduction to creating a new book from words chosen from a dictionary) is misleading, and a better analogy is the pairwise random selection of short stories from two (very long) anthologies to form a new anthology. -- Moon calls them Fortran Machines and Lisp Machines, but I would prefer to call them fuzzy mammals and pterodactyls myself. --- Richard P. Gabriel -- Wayne Throop <the-known-world>!mcnc!rti-sel!dg_rtp!throopw