A stroke occurs when blood flow to a part of the brain stops. A stroke is sometimes called a brain attack.. If blood flow is cut off for longer than a few seconds, the brain cannot get nutrients and oxygen. Brain cells can die, causing lasting damage.
A cell is said to be homozygous for a particular gene when identical alleles of the gene are present on both homologous chromosomes. The cell or organism in question is called a homozygote. True breeding organisms are always homozygous for the traits that are to be held constant.
Best Answer: Heterozygous is when you have 2 different alleles for a certain characteristic: e.g. You could have a gene for brown eye colour on one chromosome and a gene for blue eyes on the other. In this case the dominant gene of the 2 would be expressed in the individual. Homozygous dominant is when the 2 alleles are the same and they are the dominant form of the gene. e.g. 2 brown eye genes BB Homozygous recessive is when the 2 alleles are the same and are the recessive form of the gene bb. Source(s): Chelsey Kimble Â· 7 years ago.