9700_s17_qp_12
A paper of Biology, 9700
Questions:
40
Year:
2017
Paper:
1
Variant:
2
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13
Proteins in the cell surface membranes of human cells and mouse cells were labelled with fluorescent dyes. The human cells were labelled with a red dye and the mouse cells were labelled with a green dye. A human cell and a mouse cell were then fused to form a hybrid cell. At first the different dyes remained separate. After 40 minutes the two dyes were evenly distributed in the hybrid cell surface membrane. What explains this observation?
4. Cell membranes and transport  →  4.1. Fluid mosaic membranes
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18
The bacterium Escherichia coli divides once every 50 minutes at 36 °C. E. coli were grown on a medium containing only heavy nitrogen, 15N, until all of the bacterial DNA contained heavy nitrogen (0 minutes). Some of the bacteria were moved from a heavy nitrogen medium and cultured in a medium with only light nitrogen, 14N. Some bacteria were collected after each of three generations. Their DNA was extracted and centrifuged. Hybrid DNA contains heavy and light nitrogen. The diagram shows the possible positions (upper, middle and lower) of the bands of DNA. The actual positions of bands in the first two samples are shown...
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
19. Genetic technology  →  19.1. Principles of genetic technology
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24
An aphid, such as a greenfly, uses a tubular mouthpart called a stylet to feed on nutrients in the plant. It inserts the stylet through the surface of a stem or leaf. When a stylet is cut near the aphid’s head, leaving the stylet in the plant, a liquid with a low water potential continues to flow out of the plant. Which statement explains this?
14. Homeostasis  →  14.2. Homeostasis in plants
15. Control and coordination  →  15.2. Control and coordination in plants
7. Transport in plants  →  7.1. Structure of transport tissues
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