1. Bones injured: the skull. The cranium consists of the facial cranium and the brain cranium. In the facial cranium, there may be injured the mandible, maxilla, nasal bones. In the brain skull, the frontal, occipital, temporal or parietal bones may be injured. It depends on the type of the gun and bullet power whether the bullet will only enter the cranium (and damage only one of the paired bones) or exit (and damage more bones). The facial skull contains the eyeballs, the jaws encircle the mouth with teeth and the tongue, and the temporal bones encompass the medium ears and vestibular organs. The brain skull protects the brain: the cortex, the white matter, the cerebellum and the brainstem.
2. DNA gene name: challenge. Challenge gene DNA strand TAC TAC TTT GAC TTG GTC ATT. DNA antistrand ATG ATG AAA CTG AAC CAG TAA. DNA strand TAC TAC TTT GAC TTG GTC ATT. Messenger RNA AUG AUG AAA CUG AAC CAG UAA. Amino acid chain Methionine Methionine Lysine Leucine Asparagine Glutamine stop. Protein name: challenge.
3. Step 1: The sample taken for PCR may be contaminated with exogenous or unwanted DNA, thus spurious products may give inappropriate results. The plastic bags for PCR must be checked carefully and cleaned form any other contaminants. At this step, it is also important to start with an appropriate primer and to work in a carefully prepared buffer. Step 2: Agarose gel may be too dense for big DNA strands, so it may take a long time to separate two similar DNA samples. The technician must be patient enough. The quality of the gel itself is the key point of separation. It needs to prepared, loaded and treated properly, otherwise the electrophoresis sample fails to be adequate. Step 3: if a poor dye that bonds to DNA in the gel is used, the brightness may be reduced. Moreover, some dyes are unstable it time, so if the picture is not photographed in time, the late picture will be inaccurate.
4. Case # 3421. Analysis: Suspect A sample has 6 fragments, and a careful inspection shows that all of them (4, 6, 10, 14, 16 and 24 base pairs) match the crime sample. The 18 base pair fragment in #2 and #6 is very tiny, but still can be detected. The 14 and 16 base pairs fragment in #9 do not match the control ladder (might be because of the gel irregularities), however, can be traced to #6. Fragments from suspected B (#4, #5) and suspected C (#7, #8) correspond to the control ladder well, these are not artifacts, but they are in minority fragments comparing to suspected A.