Answer my Question NOW!!!!!!!!!!!
In the space below, write a description of the connection between molecules and traits and reproduction.
Answers
The classical principles of genetics were deduced by Gregor Mendel in 1865, on the basis of the results of breeding experiments with peas. Mendel studied the inheritance of a number of well-defined traits, such as seed color, and was able to deduce general rules for their transmission. In all cases, he could correctly interpret the observed patterns of inheritance by assuming that each trait is determined by a pair of inherited factors, which are now called genes. One gene copy (called an allele) specifying each trait is inherited from each parent. For example, breeding two strains of peas—one having yellow seeds, and the other green seeds—yields the following results . The parental strains each have two identical copies of the gene specifying yellow (Y) or green (y) seeds, respectively. The progeny plants are therefore hybrids, having inherited one gene for yellow seeds (Y) and one for green seeds (y). All these progeny plants (the first filial, or F1, generation) have yellow seeds, so yellow (Y) is said to be dominant and green (y) recessive. The genotype (genetic composition) of the F1 peas is thus Yy, and their phenotype (physical appearance) is yellow. If one F1 offspring is bred with another, giving rise to F2 progeny, the genes for yellow and green seeds segregate in a characteristic manner such that the ratio between F2 plants with yellow seeds and those with green seeds is 3:1
The first insight into the relationship between genes and enzymes came in 1909, when it was realized that the inherited human disease phenylketonuria results from a genetic defect in metabolism of the amino acid phenylalanine. This defect was hypothesized to result from a deficiency in the enzyme needed to catalyze the relevant metabolic reaction, leading to the general suggestion that genes specify the synthesis of enzymes.
Clearer evidence linking genes with the synthesis of enzymes came from experiments of George Beadle and Edward Tatum, performed in 1941 with the fungus Neurospora crassa. In the laboratory, Neurospora can be grown on minimal or rich media similar to those discussed in Chapter 1 for the growth of E. coli. For Neurospora, minimal media consist only of salts, glucose, and biotin; rich media are supplemented with amino acids, vitamins, purines, and pyrimidines. Beadle and Tatum isolated mutants of Neurospora that grew normally on rich media but could not grow on minimal media. Each mutant was found to require a specific nutritional supplement, such as a particular amino acid, for growth. Furthermore, the requirement for a specific nutritional supplement correlated with the failure of the mutant to synthesize that particular compound. Thus, each mutation resulted in a deficiency in a specific metabolic pathway. Since such metabolic pathways were known to be governed by enzymes, the conclusion from these experiments was that each gene specified the structure of a single enzyme—the one gene-one enzyme hypothesis. Many en-zymes are now known to consist of multiple polypeptides, so the currently accepted statement of this hypothesis is that each gene specifies the structure of a single polypeptide chain.