Discuss how only one blocked metabolic pathway, such as the one leading from phenylalanine, has the potential to cause many different disorders
What will be an ideal response?
In a metabolic pathway, the product of one reaction serves as the substrate for the next reaction. If a mutation shuts down an enzyme that performs one step in a pathway, all the reactions beyond that point are also shut down, because there is no substrate available for reactions beyond the one that is blocked. If one reaction in a pathway is shut down, it can also result in the toxic accumulation of products leading up to the block. In the case of the phenylalanine pathway, normally, phenylalanine is converted to tyrosine, and from there into many other compounds. A metabolic block caused by a mutation in the gene that encodes the enzyme phenylalanine hydroxylase prevents the conversion of phenylalanine to tyrosine. People homozygous for this mutation have the phenotype of phenylketonuria (PKU). But other genetic disorders such as genetic goitrous cretinism, alkaptonuria, and albinism are also produced by mutations in genes that encode other enzymes in this pathway.
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A. chemoautotrophs. B. chemoheterotrophs. C. photoautotrophs. D. photoheterotrophs.
Match the following items with the correct phrases.
_______1. Immune complex reactions; antigen-antibody complexes become deposited in tissue (e.g., the glomeruli of the kidneys), resulting in inflammatory damage. _______2. Anaphylactic reactions; examples include hayfever symptoms, hives, asthma, and the anaphylactic shock that could follow a bee sting or administration of penicillin. _______3. Cell-mediated reactions; antibodies don't play a major role. _______4. Cytotoxic reactions; involve the lysis of cells; the adverse reactions that follow incompatible blood transfusions are an example. a. type I hypersensitivity reactions b. type II hypersensitivity reactions c. type III hypersensitivity reactions d. type IV hypersensitivity reactions
An individual with nonidentical alleles for a gene is called ________ for that gene
a. recessive b. heterozygous c. hemizygous d. homozygous
Which of the following are in order from
primary producer to 4th trophic level? a. grass: coyote: bird: grasshopper b. coyote: bird: grasshopper: grass c. bird: grasshopper: grass: coyote d. grass: grasshopper: bird: coyote e. none of these