b

e

An unfolded protein does not have a three-dimensional shape and so will not be able to function, as three-dimensional shape is critical for protein function.

If the regulatory sequence is mutated such that its function is impaired, the gene won’t be expressed properly. If less mRNA is produced, there will be less protein, leading to a deficiency in overall antithrombin activity. If the coding sequence has a mutation that leads to a change in the amino acid sequence, the protein may have a different three-dimensional shape, reducing its activity.

This statement is not accurate. Chromosomes contain genes, and genes encode proteins. A possible rewrite: “A chromosome contains many genes. Each gene encodes one or more proteins.”

c

RNA polymerase (N); ribosome (C); tRNA (C); mRNA (C) (mRNA is made by transcription in the nucleus, but it acts in translation in the cytoplasm)

c

d

It is likely that the regulatory region is not working properly. If the regulatory region is not working properly, the normal amount of protein won’t be produced. As long as the coding sequence is normal, what protein is produced will function, but there won’t be enough of it. It is also possible that one copy of the antithrombin gene is altered in either or both of the regulatory or coding regions, and that the other copy is completely normal. In this case, there will be normal protein produced (at lower levels) from a single copy rather than from two copies.

In order to increase the amount of antithrombin produced, the regulatory sequence should be altered to increase the level of gene expression. Increasing gene expression by altering the regulatory region will increase the amount of mRNA, which in turn will increase the amount of protein produced.

a: If RNA polymerase cannot bind to the regulatory sequence, the gene will not be expressed. No mRNA will be produced, and therefore no protein. b: A change in the coding sequence that changes the amino acid sequence of the protein can change the shape and function of the protein. There may be normal amounts of protein present, but it may not function. c: A change in the regulatory sequence that increases the amount of gene expression will increase the amount of protein present because of the increased amount of mRNA present. The protein will function normally, but because there is now more of it, the overall activity may increase. d: If the regulatory sequence is changed to increase levels of gene expression, more protein will be produced. But if the coding sequence is altered, the protein expressed will not function properly, resulting in an increase in the amount of nonfunctional protein.

e

a: The construct is present in every cell, as it was introduced into the embryo. b: The construct is expressed only in mammary cells, because its regulatory region is specific for expression in mammary cells.

The beta-casein gene (because of its regulatory sequence) is expressed only in mammary cells. Because this regulatory sequence directs expression only in mammary cells, it will direct expression of the protein to be released in milk.

In order to express a non–skin cell gene in skin cells, the gene must be controlled by a regulatory sequence from a skin cell gene. In this case, the regulatory sequence of the melanin gene would drive the expression of another gene in skin cells. In order to produce melanin in yeast cells, a yeast gene regulatory region should be connected to the melanin gene. This would cause the melanin gene to be expressed in yeast.

a: In order to express insulin in the tears of goats, the lysozyme gene regulatory sequence would be needed to drive the expression of the insulin gene. b: In order to express recombinant human antithrombin in goat saliva, the amylase gene regulatory region (which drives expression in saliva) would have to be connected to the human antithrombin gene. c: Both approaches will lead to expression of the desired protein in the desired place—in tears or saliva. But neither of these secretions produces as much volume as milk. Expressing the proteins in milk will result in a product that is easily obtained in large quantities.

In the case of goat cheese, the goat’s milk does not include a foreign protein encoded by a transgene. The production of cheese from goat’s milk does not require genetic modification.

Therapeutic proteins that have to be isolated from blood products or animal organs have several disadvantages. There is a risk of contamination with blood-borne pathogens or zoonotic viruses (those found in other animals that can infect humans)—this is a safety concern. The process often takes a huge volume of blood or organs, requiring many donors or the sacrifice of many animals, and these resources may not always be available in sufficient quantity, affecting the ability of the company to produce sufficient quantity of the drug. Proteins from other animals may not be exactly identical to the human version, so may not be as effective as the human version. Often, the purification process is very elaborate and lengthy, making the purification and the final product very expensive. Thus genetic engineering that establishes transgenic animals that produce large quantities of the human protein in their milk is attractive, because this method circumvents many of these concerns. Of course, some may object to genetically engineering another organism for human purposes, and there are regulations concerning the process that companies must comply with.

a: The gene construct would have to have a bacterial gene regulatory region attached to the human insulin coding region. b: To produce human insulin in goat’s milk, the construct would have to have a regulatory region from a gene expressed in goat’s milk (e.g., beta-casein) attached to the coding region of the human insulin gene. c: A recombinant form of the insulin gene would not be necessary to genetically modify a human to express insulin if the expression were to take place in the pancreas. The insulin gene regulatory region will allow the expression of the insulin gene in the pancreas. If insulin expression were desired in some other tissue, then a regulatory region specific for that tissue (instead of the natural pancreas gene regulatory region) would be required.