8.4.3 Genetic fingerprinting ( Topic 8 The control of gene expression )

Question 1

What are variable number tandem reports (vNTRs)

Answer 1

• repeating sequences of nucleotides / bases
• found within non coding sections of DNA at many sites throughout an organisms genome

Question 2

why are VNTR: useful in genetic fingerprinting

Answer 2

• probability of two individuals having the same VNTrs is very low
• as an organisms genome contains many VNTRs and lengths at each loci differ between individuals

Question 3

Explain how genetic fingerprinting can be used to analyse DNA fragments

Answer 3

1) extract DNA from sample and amplify by PCR
2) Cut DNA at specific base sequences / recognition sites using restriction enzymes
3) Separate VNTR fragments according to length using gel electrophoresis
4) Transfer to a nylon membrane and treat to form single strand with exposed bases
5) Add labelled DNA probes which hybridise / bind with complementary VNTRs
6) To show bound probe , expose membrane to UV light if a fluorescently labelled probe was used or use autoradiography if a radioactive probe was used

Question 4

compare and contrast genetic fingerprinting with genetic screening

Answer 4

• Bith use PCR to amplify DNA sample
• Both use electrophoresis to separate DNA fragments
• bith use labelled DNA probes to visualise specific DNA fragments
• genetic fingerprinting analyses VNTRs whereas genetic screening analyses specific alleles of a gene

Question 5

Explain how genetic fingerprinting can be used to determine genetic relationships

Answer 5

• more closely related organisms have more similar VNTRs so more similarities in genetic fingerprints
• paternity testing - father should share around 50% of VNTRs / bands with child

Question 6

Explain how genetic fingerprinting can be used to determine genetic variability within a population

Answer 6

Differences in VNTRs arise from mutations , so more differences show greater diversity within a population

Question 7

Explain the use of genetic fingerprinting in the fields of forensic science , medical diagnosis , animal and plant breeding

Answer 7

forensic science :
- compare genetic fingerprint of suspect to genetic fingerprint of DNA at crime scene
- if hands match , the suspect was likely present at the crime scene
Medical diagnosis:
- some VNTRs patterns are associated with an increased risk of certain genetic disorders
Animal and plant breeding :
- Shows how closely related 2 individuals are so that inbreeding can be avoided
- breed pairs with dissimilar genetic fingerprints