Question

Drag each statement below to classify it as true or false to review the studies that revealed the specifics of gene function in organisms.

Drag each statement below to classify it as true or false to review the studies that revealed the specifics of gene function in organisms. All Neurospora mutants unable to synthesize arginine contained the same mutation in a single gene. At least four genes control arginine Synthesis in Neurospora, and these acted on different enzymes in the arginine biosynthesis pathway. Vernon Ingram found that sickle-cell anemia is caused by amino acid substitutions at several points in the hemoglobin B chain. A collection of biochemical studies showed that a single phenotype can result from only one underlying mutation. Beadle and Tatum hypothesized that each gene produces a single enzyme. Archibald Garrod studied human hereditary metabolic disorders and concluded that each one is caused by the lack of an enzyme needed for a particular biochemical Genes specify both the identity and the order of amino acids in a polypeptide chain. Beadle and Tatum found that some mutations in Neurospora produced organisms (auxotrophs) that could not manufacture certain nutrients A hypothesis that one gene can produce several enzymes resulted from the observation that an of more than one chain of amino acids. True False Reset

Answer 1

True:

1. Beadle and Tatum proved that each gene produces a single enzyme. Using their experiments on Neurospora, they gave the one gene one enzyme hypothesis.
2. Beadle and Tatum found that some mutations in Neurospora produced organisms (auxotrophs) that could not manufacture certain nutrients. During their work, they mutatgenize the spores by exposing them to X-rays. Each of the spore was then grown on a complete medium first. Later, part of each colony was transferred onto minimal medium. If the colony did not grow on minimal medium, it was an auxotroph (deficient in certain nutrients).
3. Genes specify both the identity and the order of amino acids in a polypeptide chain. Genes have coding DNA sequence that is transcribed to an mRNA. mRNA has a sequence of codons that are translated to polypeptide.
4. Archibald studied human hereditary metabolic disorders and concluded that each one is caused by the lack of an enzyme needed for a particular biochemical reaction. Sir Achibal Garrod was the physician who pioneered research in the field of inborn errors of metabolism. He initially worked on alkaptonuria and later on is known to have worked on cystinuria, albinism and pentosuria. His hypothesis was later proved by Beadle an Tatum.
5. Atleast four genes control arginine synthesis in Neurospora and these acted on different enzymes in the arginine biosynthesis pathway. The pathway to synthesize arginine from glutamate contains about 8 steps, each catalyzed b an enzyme.

False

1. All Neurospora mutants unable to synthesize arginine contained the same mutation in a single gene. Since the mutations were randomly done, it is difficult to expect same mutation everytime in the gene. Moreover, the metabolic pathway to synthesize arginine comprises of many steps. If enzyme at any of those steps are mutated that would also make the Neurospora an auxotroph for Argnine.
2. A collection of biochemical studies showed that a single phenotype can result from only one underlying mutation. Mutation can occur at different positions in the same gene rendering is non-functional. Morever, a phenotype can be a result of the action of product of multiple genes. Mutation in any one or more of these genes can result in same phenotype.
3. A hypothesis that one gene can produce several enzymes resulted from the observation that an enzyme may be made up of more than one chain of amino acids. This is an incorrect statement. A gene can produce many polypeptides due to alternative splicing or such processes. But it can not answer for many enzymes. Enzymes can be made of more than on polypeptide chain, each can be coded by a different gene.
4. Vernon Ingram found that sickle cell anemia is caused by amino acid substitutions at several points in the hemoglobin beta chain. This is an incorrect statement since he discovered that only one mutation in beta chain at position 6 changed glutamic acid to valine and was responsible for this disease.