Genetic Fingerprinting

Question 1

describe the process of Gel Electrophoresis

Answer 1

• DNA samples are placed in separate wells at the top of the gel
• the DNA fragments in each sample are separated according to size (smaller moves further and faster) when a positive electric charge is applied

Question 2

describe the process of genetic fingerprinting

Answer 2

• PCR used to amplify the sample DNA and restriction endonucleases are used to cut amplified DNA into fragments
• DNA fragments are then separated using Gel Electrophoresis
• DNA fragments are then treated (using alkali) to form single strands and then are transferred to a nylon membrane
• radioactively labelled DNA probes are added which are complementary to the VNTRs and therefore bind to them via DNA hybridisation
• nylon membrane is placed on X-ray or photographic film and the position of the radioactively labelled fragments is revealed therefore obtaining the genetic fingerprint

Question 3

what is a DNA ladder

Answer 3

a lane of DNA fragments of known sizes used to calculate the size of DNA fragments in the unknown samples

Question 4

what are DNA primers

Answer 4

• short single stranded molecules of DNA which provide a starting sequence for DNA polymerase

Question 5

why are DNA primers important

Answer 5

• DNA polymerase cannot begin at a single stranded starting point and also help prevent the original DNA strands from joining back together

Question 6

what are DNA probes

Answer 6

• short single stranded molecules of DNA that are radioactively or fluorescently labelled and are used to identify or locate known sequences of DNA

Question 7

what is DNA hybridisation

Answer 7

• a process in which two complementary single stranded DNA molecules bond together to form a double stranded molecule

Question 8

name 3 uses of genetic fingerprinting

Answer 8

• forensic science - can be used to compare DNA samples from the crime scene and a suspect
• medical diagnosis - certain diseases involve unique patterns of several alleles and can be identified more readily by genetic fingerprinting
• determining genetic relationships - the closer related organisms are, the more similar their VNTRs will be

Question 9

what is gene therapy

Answer 9

• the introduction of functional copies of an allele into an organism which possesses defective alleles of the same gene

Question 10

what is the difference between somatic and germline therapy

Answer 10

somatic therapy - not heritable as it is not in the gametes
germline therapy - heritable as it is in the gametes (currently illegal)