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1 State the correct term for the following definitions:

a determining the order of bases on a section of DNA

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b producing a unique digest pattern of the DNA from an individual

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c replacing a faulty gene in a person’s body cells with a healthy allele

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d creating many copies of a gene in the lab without using bacteria as hosts

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e study of the moral dimension and measurement of benefits and problems of a technology

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2 Describe the difference between:

a genetic manipulation and artificial selection of crop plants

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b genomics and proteomics

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c farming and pharming.

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3 a Genetic modification of organisms uses a ‘toolkit’ that includes:

▪ enzymes that cut DNA

▪ enzymes that join sections of DNA together

▪ vectors that introduce DNA into new host cells.

Some of the enzymes and vectors that are important in genetic modification are given an identifying letter in Table 1.

| |Enzymes | | |Vectors |

|A |reverse transcriptase | |J |plasmid |

|B |DNA polymerase | |K |virus |

|C |DNA ligase | |L |Agrobacterium tumefaciens |

|D |restriction endonuclease | | | |

|E |RNA polymerase | | | |

Table 1

Select one correct letter from Table 1 to fit each of the following statements.

An enzyme that cuts DNA ..............

An enzyme that joins sections of DNA together ...............

A vector to introduce foreign DNA into bacteria ...............

A vector to introduce foreign DNA into plant cells ...............

A vector to introduce foreign DNA into animal cells ...............

(5 marks)

b Outline one potential benefit and one ethical concern of each of these examples of genetic modification.

• soya modified for resistance to insects

• humans having somatic gene therapy treatment for a genetic disease

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OCR Biology A, January 2012, Specimen paper

4 a The polymerase chain reaction, PCR, is used to amplify DNA that can only be obtained initially in small amounts.

Outline two situations where it might only be possible to obtain DNA in small amounts but there is a need to amplify more of it.

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b Table 2 shows the temperatures used at different stages of the PCR reaction.

|Time/min |Temperature/°C |

|0 |72 |

|1 |90 |

|2 |90 |

|3 |55 |

|4 |55 |

|5 |72 |

|6 |90 |

Table 2

Explain what happens to DNA molecules:

i between 1–2 minutes

ii between 3–4 minutes

iii between 4–5 minutes

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c Use your knowledge of the technique of PCR to explain two problems that may occur with the method.

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d i One complete cycle of PCR takes five minutes. Assuming that there are 50 copies of the double-stranded target DNA molecule at time zero, calculate the number of DNA molecules after 45 minutes.

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ii After one hour the number of DNA molecules is 204 800. Express this number as a base 10 logarithm and explain the purpose of doing this. Give your answer to three decimal places.

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5 Gel electrophoresis can be used to analyse DNA. Figure 1 shows the results of an electrophoresis experiment.

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Figure 1

The DNA used for the experiment was 15 kilobase pairs long. It was incubated before electrophoresis with either:

• BamH1

• EcoR1

• both BamH1 and EcoR1.

The three samples were then mixed with a loading dye and placed in the wells on the gel. A current was then applied via electrodes dipped into the buffer solution in the gel tray.

a Explain the function of:

i the loading dye

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ii the buffer solution

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iii BamH1 and EcoR1

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b Use Figure 1 to state:

i the number of restriction sites for BamH1

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ii the sizes of the DNA fragments produced by EcoR1

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c Evaluate the usefulness of this method of restriction fragment DNA profiling in the diagnosis of inherited disease.

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21 Manipulating genomes test

Name ________________

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