LIFESCI 15 Lecture Notes - Lecture 9: Silent Mutation, Noncoding Dna, Peptide
2/6/18
I. DNA Fingerprinting
II. Individual differences in DNA → STRs
III. STR analysis and DNA fingerprinting
IV. Difficulties and controversies
DNA Fingerprinting
- Why are we interested in DNA fingerprinting?
o Real fingerprints not left behind in many crimes
o They are essentially unique
- What are the uses?
o Solve unsolvable crimes
o Resolve paternity issues
o Can prove innocence of people unjustly convicted
o Immigration
- DNA is a log seuee of lettes that a the ifo of ho to uild oleules fo the od
o A, T, G, or C
o Thymine, guanine, adenine, cytosine
- Ho uh spellig diffeee is thee etee idiiduals?
o Almost none; 99.9% identical
o Different enough; 3 million different base pairs
#1: on average, individuals differ in their DNA sequence at 0.1% of their bases: 3 million differences out of 3
billion base pairs
Individual Differences in DNA → STRs
- The fundamental question: we have DNA from several samples. How can we tell if the DNA came from
the same person?
- What are STRs?
o Short tandem repeats
o Repeating units 4-5 nucleotides long
o Repeats some different number of times in every person
o Does’t ode fo ee olo, hai tpe… just sits thee
#2: For an STR locus → many (2 or 3 dozen or even more!) alleles exist within the population but each
individual can only have 2 of them
- Comparing STR Loci
o Choose features for which individuals vary a lot
o Copae DNA saples fo those featues if the ae the sae at all of the…
o The samples come from the same individuals
STR Analysis and DNA Fingerprinting
- Creating a DNA Fingerprint
1. The DNA fragment containing each STR region is amplified using PCR. This results in huge
numbers of those fragments
2. The fragments are separated by size, using electrophoresis
a. Use gel
- Human paternity testing
o Analyzing one locus
o What do the bands represent?
o Which pair of people are the parents of each?
find more resources at oneclass.com
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Document Summary
Why are we interested in dna fingerprinting: real fingerprints not left behind in many crimes, they are essentially unique. What are the uses: solve unsolvable crimes, resolve paternity issues, can prove innocence of people unjustly convicted. Dna is a lo(cid:374)g se(cid:395)ue(cid:374)(cid:272)e of (cid:862)lette(cid:396)s(cid:863) that (cid:272)a(cid:396)(cid:396)(cid:455) the i(cid:374)fo of ho(cid:449) to (cid:271)uild (cid:373)ole(cid:272)ules fo(cid:396) the (cid:271)od(cid:455: a, t, g, or c, thymine, guanine, adenine, cytosine. Ho(cid:449) (cid:373)u(cid:272)h (cid:862)spelli(cid:374)g(cid:863) diffe(cid:396)e(cid:374)(cid:272)e is the(cid:396)e (cid:271)et(cid:449)ee(cid:374) i(cid:374)di(cid:448)iduals: almost none; 99. 9% identical, different enough; 3 million different base pairs. #1: on average, individuals differ in their dna sequence at 0. 1% of their bases: 3 million differences out of 3 billion base pairs. The fundamental question: we have dna from several samples. What are strs: short tandem repeats, repeating units 4-5 nucleotides long, repeats some different number of times in every person, does(cid:374)"t (cid:272)ode fo(cid:396) e(cid:455)e (cid:272)olo(cid:396), hai(cid:396) t(cid:455)pe just sits the(cid:396)e.
