User:Georgehe4/sandbox

Measuring Variation

Genetic Human Variation

Measurements of genetic human variation have primarily been focused on a variety of factors including:

DNA Fingerprinting

Main article: DNA Fingerprinting

(DNA profiling), whereby a DNA fingerprint is constructed by extracting a DNA sample from body tissue or fluid. Then, it is segmented using restriction enzymes and each segment marked with probes then exposed on X-ray film. The segments form patterns of black bars;the DNA fingerprint. DNA Fingerprints are used in conjunction with other methods in order to individuals information in Federal programs such as CODIS (Combined DNA Index System for Missing Persons) in order to help identify individuals

Mitochondrial DNA

Main article: Mitochondrial DNA

(Mitochondrial DNA), which is only passed from mother to child. The first human population studies based on mitochondrial DNA were performed by restriction enzyme analyses (RFLPs) and revealed differences between the four ethnic groups (Caucasian, Amerindian, African, and Asian). Differences in mtDNA patterns have also been shown in communities with a different geographic origin within the same ethnic group

Allozymic Variation

Main article: Allozymic Variation

Allozymic Variation, a source of variation that identifies protein variants of the same gene due to amino acid substitutions in proteins. After grinding tissue to release the cytoplasm, wicks are used to absorb the the resulting extract and placed in a slit cut into a starch gel. A low current is run across the gel resulting in a positive and negative ends. Proteins are then separated by charge and size, with the smaller and more highly charged molecules moving more quickly across the gel. This techniques does underestimate true genetic variability as there may be an amino acid substitution but if the amino acid is not charged differently than the original no difference in migration will appear it is estimated that approximately 1/3 of the true genetic variation is not expressed by this technique.

Structural Variation

Main article: Structural Variation

(Structural variation), which can include insertions, deletions, duplications, and mutations in DNA. Within the human population, about 13% of the human genome is defined as structurally variant.

Phenotypic Variation

Main article: Phenotypic Variation

Phenotypic Variation (Phenotype#Phenotypic variation), which accounts for both genetic and epigenetic factors that affect what characteristics are shown. For applications such as organ donations and matching, phenotypic variation of blood type, tissue type, and organ size are considered.