Forensic DNA Study

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Author:
Barto22
ID:
136932
Filename:
Forensic DNA Study
Updated:
2012-02-22 06:26:09
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Forensics
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Description:
Notes on DNA, Refraction, and Blood Splatters
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  1. Nucleotides?
    The subunits of DNA, which are 3-part structures that make up nucleic acid molecules
  2. 3 parts of a nucleotide?
    Deoxyribose, phosphate group, and nitrogenous base.
  3. Purine Bases?
    Adenine and Guanine (2 Carbon Rings)
  4. Pyrimidine Bases?
    Cytosine and Thymine (1 Carbon ring)
  5. Backbone of Double Helix
    Sugar & Phosphate
  6. Complimentary Bases?
    • Cytosine with Guanine
    • Thymine with Adenine
  7. Genes?
    Codes for some kind of trait. Tell the cell to make other molecules called proteins. A segment of DNA.
  8. Allele?
    an alternative form of a single gene passed from gen. to gen.
  9. Genotype?
    An organism's allele pairs
  10. Phenotype?
    Observable characteristics or outward expression of an allele pair.
  11. Chromosomes?
    • The human body has 46 chromosomes.
    • Each parent contributes 23.
    • 22 are autosomes, 1 is the sex chromosome.
    • Females have two X chromosomes, males have one X and Y chromosome.
  12. Homologous Chromosomes?
    the chromosomes that make up a pair, one from each parent.
  13. Mitochondrial DNA
    • DNA found in mitochondria of cell.
    • Inherited only from the mother.
  14. Uses of DNA?
    • No two people have the same DNA, except twins.
    • DNA evidence has been used to investigate crimes, establish paternity, identify victims of war, and large scale disasters.
  15. Human Genome?
    • Total amount of DNA in a cell, contained in chromosomes and mitochondria.
    • DNA in chromosomes contains approx. 3 billion base paris.
    • The genome for humans is approx. 100,000 genes in size.
  16. DNA Fingerprinting, who made it?
    Dr. Alec Jeffreys in 1984
  17. Who made the PCR technique?
    Dr. Kary Mullis in 1985
  18. Tandem repeats?
    variations that occur in the non-coding regions of the DNA that consist of unique patterns of ened to end repeated base sequences.
  19. Usefulness of tandem repeats?
    • # and location are unique in each individual, creating a DNA profile.
    • These repeats may be studied to aid in identification of individuals.
    • The more locations on an individuals DNA examined, the higher probability of identifying the individual.
  20. Variable Number of Tandem Repeats (VNTRs)?
    • The # of copies of the same repeated base sequence in the DNA.
    • Can be 9 - 80 bases long.
  21. Short Tandem Repeats (STR)?
    • Usually only 2 - 5 nase pairs in length.
    • More prefereed as they are more accurate and can be used with small or partially degrade samples of DNA.
    • VNTR's are longer and require DNA to be longer, making it difficult to separate the VNTR sequence.
  22. Uses for a DNA profile?
    • Tissue Matching
    • Inheritance Matching
  23. DNA Directionality?
    • one of the parent strands in DNA run in a 5' to 3' direction while the other runs in a 3' to 5' direction.
    • The numbers refer to the carbon number of the deoxyribose ring.
  24. Primers and Polymerase?
    • DNA primers - short segments of DNA that are complimentary to target DNA.
    • DNA polymerase - enzyme that binds free-floating nucleotides tot eh complimentary bases on a DNA strand.
    • Restriction Enzymes - proteins that recognize a particular sequence in DNA and cut the DNA apart at that location.
  25. Steps in DNA Fingerprinting?
    • 1. Extraction - DNA is removed from nucleous of cell
    • 2. Restriction Fragments - cut apart DNA at specific sites
    • 3. Amplification - Duplicate the DNA
    • 4. Electrophoresis - DNA fragments separated by electric field.
  26. Steps in PCR?
    • 1. Mis primers with DNA, DNA polymerase, buffers and nucleotides.
    • 2. Heat the mixture to boiling to denature the DNA
    • 3. Allow mixture to cool.
    • 4. At this point, the DNA would normally rezip to form the origional double-stranded molecule, but the primers attach to DNA instead.
    • 5. DNA polymerase will now bind nucletides to the end of each primer to complete the complimentary strands.
    • 6. There are now to complete copies of DNA.
    • 7. The entire process is repeated to create millions of fragments.
  27. CODIS?
    • Combined DNA Index System: an electronic database of DNA profiles
    • Individuals convicted of certain crimes (rape, murder, child abuse) have their DNA profiles entered into the database.
  28. Refraction equation?
    n1sin(a1) = n2sin(a2)

    • n1 and n2 = refractive indexes
    • a1 and a2 = incidident angle/refracted angle
  29. Blood Splatter?
    • Take length and width of splatter
    • Inverse sin of (w/l)
    • tan(bsa) = h / d

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