DNA Sequencing and DNA Profiling

Technology 1 · reading the base order

In 1986, Alec Jeffreys' laboratory received blood samples from 5,511 men in Leicestershire, England, and ran each through RFLP DNA fingerprinting, a technique Jeffreys had only developed in 1984. The technique did not read entire genomes; it compared the lengths of DNA fragments produced by restriction enzymes cutting at specific variable repeat regions. Two samples with identical fragment patterns at multiple independent loci were statistically near-certain to come from the same individual. The statistical reliability came from knowing how common each fragment pattern was in the general population, the same allele frequency logic this lesson covers.

If the sequence is known, specific mutations, SNPs and gene variants can be identified directly. This is powerful for investigating inherited disorders, comparing species, and analysing how populations differ at the DNA level.

DNA sequencing = determining the exact nucleotide order of a DNA region. When the sequence is known, specific mutations, SNPs and inherited variants can be identified directly. Useful for: inherited disorder investigation, species comparison, population-level DNA difference analysis.

Pause, copy the highlighted DNA sequencing definition and its three uses into your book.

Technology 2 · pattern comparison, not full reading

We just saw that DNA sequencing reads the actual base order to identify specific variants. That raises a question: if you just need to compare whether two samples match, not read every base, what technology is more efficient? This card answers it → DNA profiling, which compares patterns at selected variable regions rather than reading the whole genome.

DNA profiling does not normally read the full base order of the whole genome. Instead, it compares patterns at selected DNA regions that vary between individuals. This allows samples to be distinguished or matched more efficiently.

DNA profiling = comparing patterns at selected variable DNA regions to distinguish or match samples. It shows similarity, difference, and possible inheritance links efficiently. A profile is NOT a full genome sequence, it uses marker patterns, not the complete base order.

Add the highlighted DNA profiling definition and the "NOT a full sequence" distinction to your notes.

Key distinction · base order vs pattern

We just saw that DNA profiling compares selected marker patterns rather than reading the whole genome. That raises a question: how do sequencing and profiling complement each other, when would you use one vs the other? This card answers it → sequencing for base-level detail and variant discovery; profiling for efficient sample matching and relatedness inference.

Both technologies can contribute to understanding inheritance patterns in populations, but the strength of the conclusion depends on what data was collected. Sequencing offers more direct molecular detail. Profiling offers efficient comparison at specific markers.

Sequencing: reads nucleotide order → identifies specific mutations/SNPs → variant discovery. Profiling: compares selected patterns → matches/distinguishes samples → relatedness/inheritance links. Both study population inheritance. Sequencing = more molecular detail; profiling = efficient comparison.

Pause, write the highlighted sequencing vs profiling comparison into your book as a two-column summary.

Module 5 focus · inheritance, not just forensics

We just saw that sequencing and profiling each excel at different question types. That raises a question: in the Module 5 context, what are these technologies actually being used to study? This card answers it → inheritance patterns across populations (disease variants, relatedness structure), not just forensic identification.

For Module 5, the important idea is not a narrow forensic storyline. The important idea is how these tools are used to investigate inheritance across groups.

Module 5 focus = inheritance across groups, not just forensics. Sequencing → identifies inherited disease-linked variants. Profiling → compares related samples/lineages. Both infer relatedness trends, not certainty from one sample alone. Keep emphasis on population inheritance and disorder investigation.

Add the highlighted Module 5 technology focus to your notes.

Worked reading · match the claim to the technology

We just saw that both technologies serve the Module 5 focus of studying inheritance patterns and population structure. That raises a question: how do we answer an exam question that asks us to choose between or evaluate sequencing vs profiling for a given scenario? This card answers it → a four-step sequence to match the claim to the technology.

Exam approach for sequencing vs profiling: 1, identify what the technology produces (base order vs marker pattern); 2, state what question it can answer; 3, link to inheritance patterns, relatedness or disease; 4, keep conclusion matched to technology's actual capability.

Pause, write the four-step exam approach for technology questions into your book.