WEILAI Online Academic assistant
WEILAI Online Academic assistant
Back to 课程

Biology_A-level_Aqa

0% Complete
0/0 Steps

  1. 1-biological-molecules

    1-1-biological-molecules-carbohydrates
    11 主题
  2. 1-2-biological-molecules-lipids
    3 主题
  3. 1-3-biological-molecules-proteins
    5 主题
  4. 1-4-proteins-enzymes
    12 主题
  5. 1-5-nucleic-acids-structure-and-dna-replication
    8 主题
  6. 1-6-atp-water-and-inorganic-ions
    4 主题
  7. 2-cell-structure
    2-1-cell-structure
    7 主题
  8. 2-2-the-microscope-in-cell-studies
    4 主题
  9. 2-3-cell-division-in-eukaryotic-and-prokaryotic-cells
    8 主题
  10. 2-4-cell-membranes-and-transport
    7 主题
  11. 2-5-cell-recognition-and-the-immune-system
    7 主题
  12. 2-6-vaccines-disease-and-monoclonal-antibodies
    6 主题
  13. 3-exchange-and-transport
    3-1-adaptations-for-gas-exchange
    6 主题
  14. 3-2-human-gas-exchange
    10 主题
  15. 3-3-digestion-and-absorption
    5 主题
  16. 3-4-mass-transport-in-animals
    6 主题
  17. 3-5-the-circulatory-system-in-animals
    8 主题
  18. 3-6-mass-transport-in-plants
    6 主题
  19. 4-genetics-variation-and-interdependence
    4-1-dna-genes-and-chromosomes
    7 主题
  20. 4-2-dna-and-protein-synthesis
    6 主题
  21. 4-3-genetic-diversity-mutations-and-meiosis
    7 主题
  22. 4-4-genetic-diversity-and-adaptation
    6 主题
  23. 4-5-species-and-taxonomy
    4 主题
  24. 4-6-biodiversity
    9 主题
  25. 5-energy-transfers-in-and-between-organisms-a-level-only
    5-1-photosynthesis-a-level-only
    5 主题
  26. 5-2-respiration-a-level-only
    7 主题
  27. 5-3-energy-and-ecosystems-a-level-only
    9 主题
  28. 5-4-nutrient-cycles-a-level-only
    4 主题
  29. 6-organisms-respond-to-changes-in-their-environments-a-level-only
    6-1-response-to-stimuli-a-level-only
    12 主题
  30. 6-2-nervous-coordination-a-level-only
    10 主题
  31. 6-3-skeletal-muscles-a-level-only
    6 主题
  32. 6-4-homeostasis-a-level-only
    11 主题
  33. 7-genetics-populations-evolution-and-ecosystems-a-level-only
    7-1-inheritance-a-level-only
    6 主题
  34. 7-2-populations-a-level-only
    3 主题
  35. 7-3-evolution-a-level-only
    5 主题
  36. 7-4-populations-in-ecosystems-a-level-only
    7 主题
  37. 8-the-control-of-gene-expression-a-level-only
    8-1-genetic-mutations-a-level-only
    2 主题
  38. 8-2-regulation-of-gene-expression-a-level-only
    11 主题
  39. 8-3-using-genome-projects-a-level-only
    4 主题
  40. 8-4-gene-technologies-a-level-only
    13 主题
  41. exam-guidance-and-skills
    essay-guidance
    3 主题
课 Progress
0% Complete

Genetic fingerprinting

  • Genetic fingerprinting (also known as DNA profiling) is a technique used to identify individuals or assess genetic relationships by analysing non-coding, variable regions of DNA, especially VNTRs (variable number tandem repeats)

    • The method allows scientists to create a genetic profile, much like a barcode, from DNA samples

  • Genetic fingerprinting uses a range of gene technologies to complete an individual’s unique genetic profile

The process of genetic fingerprinting

  1. DNA extraction

    • DNA is collected from cells (e.g. blood, saliva, hair root).

    • The DNA is then purified for analysis.

  2. Amplification by polymerase chain reaction

    • PCR is used to amplify specific VNTR regions of the DNA to obtain enough material for analysis

    • This is especially useful when only a small amount of DNA is available

  3. Restriction enzyme digestion

    • Restriction endonucleases are added to cut the DNA at specific sequences, generating fragments containing VNTRs

  4. Gel electrophoresis

    • DNA fragments are separated based on size using an agarose gel and an electric current

    • Smaller fragments travel further, creating a distinct pattern of bands

  5. DNA hybridisation

    • DNA is transferred to a nitrocellulose or nylon membrane and denatured into single strands

    • DNA probes (radioactive or fluorescent) that bind to VNTR regions are added

  6. Visualisation

    • The resulting pattern is visualised using X-ray film (for radioactive probes) or UV light (for fluorescent probes)

    • The banding pattern represents the individual’s genetic fingerprint

Determining genetic relationships

  • Offspring inherit half their VNTRs from each parent

  • By comparing the banding patterns of DNA profiles:

    • Parentage can be confirmed (e.g., paternity tests)

    • Sibling and other family relationships can be inferred

  • In inheritance disputes or immigration cases, DNA fingerprinting provides evidence of biological relationships

Determining genetic variability in a population

  • Populations with high genetic variability show many different VNTR patterns

  • Populations with low genetic diversity will show more similar or repeated banding patterns

  • This is useful in conservation biology and breeding programs to monitor genetic health

Worked Example

A DNA sample was collected at a crime scene. Investigators obtained DNA from the victim, the crime scene and three suspects. The DNA was extracted, cut with restriction enzymes, amplified using PCR, and then analysed using gel electrophoresis.

The gel electrophoresis results are shown below.

Table comparing hair samples from victim, crime scene, and three suspects, using lines to represent sample matches and differences.

Identify which suspect is most likely to have been at the crime scene. Use evidence from the gel to support your answer.

[1 mark]

Model Answer

Step 1: Read across the results from the gel electrophoresis, looking for a match between the crime scene and the suspects

Suspect 2 matches the DNA found at the crime scene in all visible bands

Examiner Tips and Tricks

In the exam, you will be expected to interpret the results of gel electrophoresis experiments used to separate DNA fragments.