Normal blood cells slide easily through narrow blood vessels. In sickle cell disease many red blood cells change to a crescent shape like a slender moon Crescent-shaped blood cells cause blockages in blood vessels These blockages decrease the transport of oxygen People with sickle cell disease often have sharp pains due to the lack of oxygen in parts of the body Some people have one sickle cell gene and one normal gene They have few defective cells and no symptoms because the sickle cell gene is recessive. How does the method of reproduction in humans result in people getting one copy of a sickle cell gene and one copy normal gene? Describe the process

The method of reproduction in humans is sexual reproduction: a type of reproduction that occurs when new organisms are produced through the coming together of genetic information from two individuals of different sexes mostly a male and a female (egg cell and the sperm). The genetic information for making the blood cells; the red blood cells genes in particular exists on chromosomes in the nucleus of the sex cells (egg and sperm cell) also called the gametes. Basically, the DNA provides instructions for the production of mostly all of the body's needs.

The genes coding for the sickle cells which is the abnormal red cell is always inherited in the recessive form meaning both parent has to possess one copy each of the defective gene in their DNA. For humans to get one copy of a sickle cell gene and one copy normal gene; it means one of the parents gametes (be it male or female) contributed the defective chromosome and the other normal gene is contributed by the other parent during copulation giving rise to an individual that is heterozygous for the trait

For example, the sperm cell with the defective gene fertilizes the egg cell that has the normal copy of the gene producing an heterozgous individual.