Diagnosis of Human Genetic Diseases Restriction enzymes , such as Hpa I were used in a study on sickle-cell anemia. The probe hybridized in normal hemoglobin with two fragments 7000 or 7600 nucleotides long. Sickle-cell hemoglobin had hybridization with a 13,000 nucleotide single sequence. A similar result has been obtained from amniocentesis studies, providing a tool to screen fetus and adult for sickle-cell. The markers where hybridization occurred are referred to as RFLPs (restriction-fragment-length polymorphisms) . The longer fragment in sickle-cell individuals is interpreted as evidence of a mutation in the recognition sequence. Two nucleotide sequences close together on the same DNA molecule tend to stay together. In the sickle-cell DNA the beta-chain hemoglobin gene has become linked with another gene that somehow alters the recognition sequence at which Hpa I hybridizes. Heterozygotes will have both long and short fragments, while a single type (short or long) will occur in homozygous dominant and recessive,
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This note was uploaded on 11/29/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.