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DNA Fingerprinting

DNA Fingerprinting. DNA Structure Review. Double stranded helix shape Basic unit is a nucleotide: Phosphate-sugar backbone Nitrogen bases hold two strands together by hydrogen bonds. A bonds with T G bonds with C Located in the nucleus. Genetics Review.

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DNA Fingerprinting

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  1. DNA Fingerprinting

  2. DNA Structure Review • Double stranded helix shape • Basic unit is a nucleotide: • Phosphate-sugar backbone • Nitrogen bases hold two strands together by hydrogen bonds. • A bonds with T • G bonds with C • Located in the nucleus

  3. Genetics Review • No two humans have identical DNA fingerprints (except for identical twins) • The A,T,G,C sequence is unique • Chromosomes are made of DNA and protein • A gene is a sequence of DNA that codes for a protein. • 1.5% of DNA in our genome codes for protein • 98.5% of DNA is “noncoding DNA” – doesn’t code for a protein (some is involved in gene regulation or gene splicing…the rest is “junk”)

  4. Genetics review continued: • There are 23 PAIRS (46 total) of chromosomes in the nucleus of EVERY cell in the human body (except for egg and sperm) • one chromosome in each pair comes from your dad, the other from your mom. • There is also mitochondrial DNA (DNA found in the mitochondria). This is inherited from your mom

  5. DNA Identification • Most of the human genome is the same in all humans (because we are human) • Variation in our sequences mostly exists in the noncoding DNA (98.5% of our DNA) • Much of it is in the form of repeated base sequences. • Everyone has unique patterns of repeated base sequences. • These base sequences have different lengths and different sequences in individuals. They are called “polymorphisms”

  6. DNA Fingerprint • Pattern of DNA fragments obtained by examining a person’s unique sequence of DNA base pairs • A DNA fingerprint is used for two main purposes: • Tissue matching (same pattern, same person) • Inheritance matching (each band of a child’s DNA fingerprint must be present in at least one parent).

  7. Sources of DNA (see Table 9-2 on pg. 339 in your book) • Saliva (envelope, toothbrush, bite wound, cup, cigarette butt) • Blood (only need a drop) • Seminal fluid (clothes, bedding) • Skin (weapon, tape) • Hair (or hair follicle) • Sweat (weapon, hat. • Mucous (tissue, cotton swab) • Ear wax (tissue, cotton swab, ear buds) • Urine (blanket, pillow, sheet)

  8. Process of Electrophoresis • Use restriction enzymes • A restriction enzyme is an enzyme that cuts DNA at specific “recognition sites” • In nature restriction enzymes protect bacteria against intruding DNA (viruses) by cutting the intruders DNA (can’t function) • Use an electrophoresis apparatus to separate the cut DNA

  9. Process of Electrophoresis continued • DNA is obtained • Copies of DNA are made using the PCR method (polymerase chain reaction). • this is just a complex way to make a ton of DNA copies • Restriction enzymes are added to cut the DNA into fragments at very specific sequences. • DNA has an overall negative charge

  10. Process of Electrophoresis continued • Put DNA into wells of gel at the negative end of the chamber • Turn on power supply • Smaller fragments will travel faster through gel, therefore they will travel the farthest in the allotted time.

  11. Shortest fragment

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