Sickle-cell anaemia

Content
Human Genetics
Human chromosomes
Determination of sex
Sex linked inheritance
Chromosomal aberrations
Dizygotic and monozygotic twins
Inborn errors in metabolism
Sickle-cell anaemia
Genetic analysis through pedigree charts
Chromosome mapping in humans (including RFLPs, etc.)
Gene transfer in mammalian cells
Chromosome mediated gene transfer
Transformation of cells with free DNA
Use of human genetics in medical science 
Genetic counseling
Amniocentesis and antenatal diagnosis
Gene therapy
Making a choice of baby's sex
DNA fingerprinting in forensic science
Sickle cell anaemia is a blood disease where the red blood cells become sickle shaped as compared with round shape in normal individual. This results into various abnormalities and may ultimately result into death. This disease is caused by a single gene, which in heterozygous condition causes moderate sickling (sickle cell trait) and in homozygous condition causes severe effect (sickle cell anaemia). It was also found that the haemoglobins of normal individual and a patient have different mobilities in an electrophoretic field (Fig. 24.4). Haemoglobin of sickle cell anaemia moves in a direction opposite to that of normal haemoglobin. Such a difference was later discovered to be due to the replacement of a single amino acid in βchain of haemoglobin (Fig. 24.5).

Electrophoretic mobilities in normal and abnormal haemoglobins.
Fig. 24.4. Electrophoretic mobilities in normal and abnormal haemoglobins.
 
Segment of β chains of normal and abnormal haemoglobin showing amino acid replacement.
Fig. 24.5. Segment of β chains of normal and abnormal haemoglobin showing amino acid replacement.