A food-packaging research team needs large quantities of an enzyme that removes oxygen from sealed packs of sliced apples. Low oxygen slows the browning of ...
Question 1 Report
A food-packaging research team needs large quantities of an enzyme that removes oxygen from sealed packs of sliced apples. Low oxygen slows the browning of the fruit. Fig. 1 shows how the team uses a circular piece of DNA from a bacterium to introduce a gene from a mould species into yeast cells. The yeast cells are grown in a fermenter, where they release the enzyme into the liquid. The enzyme is then separated and added to a gel inside the food packs.
(a) Identify the circular DNA molecule used to carry the gene into a yeast cell. [1]
(b) Describe how the yeast cells are used after they have received the gene. [3]
(c) Explain why inserting the mould gene allows the yeast cells to make the required enzyme. [3]
(d) Calculate the volume of enzyme gel needed for 240 packs if each pack needs 0.35 cm3 of gel. [2]
(e) Suggest one control the team could use to show that the enzyme gel, rather than the packaging alone, slows browning. [1]
Answer Details
(a) Plasmid [1] (b) Yeast cells are grown / cultured in a fermenter [1]; they reproduce to form many cells [1]; the enzyme is collected / extracted / purified from the culture liquid [1] (c) The inserted gene is a section of DNA containing the code for the enzyme [1]; yeast cells read / express the gene [1]; the cells join amino acids in the coded order to make the enzyme protein [1] (d) 240 x 0.35 [1] = 84 cm3 [1] (e) Use otherwise identical apple packs with gel that contains no enzyme / no gel, and compare their browning with enzyme-gel packs [1]
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