DNA - CS50x 2023

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• adenine (A), cytosine (C), guanine (G), or thymine (T).

• DNA is really just a sequence of molecules called nucleotides,

• arranged into a particular shape (a double helix).

• Each nucleotide of DNA contains one of four different bases

• If the probability that two people have the same number of repeats for a single STR is 5%

• Short Tandem Repeats (STRs).

• and the analyst looks at 10 different

• An STR is a short sequence of DNA bases that tends to repeat consecutively numerous times at specific locations inside of a person’s DNA.

• So if two DNA samples match in the number of repeats for each of the STRs, the analyst can be pretty confident they came from the same person.

• each row corresponds to an individual,

• each column corresponds to a particular STR.

• imagine that you looked through the DNA sequence for the longest consecutive sequence of repeated AGATs and found that the longest sequence was 17 repeats long. If you then found that the longest sequence of AATG is 22 repeats long, and the longest sequence of TATC is 19 repeats long, that would provide pretty good evidence that the DNA was Bob’s. Of course, it’s also possible that once you take the counts for each of the STRs, it doesn’t match anyone in your DNA database, in which case you have no match.

• forensic investigators

• chromosome

• localize

• Each nucleotide of DNA contains one of four different bases

• adenine (A), cytosine (C), guanine (G), or thymine (T)