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.
homozygous means you have two alleles with the same characteristic. example; two alleles for brown eyes. recessive means that when you have two different alleles, one of then doesn't show its trait. example; one allele for brown eyes and one allele for green eyes gives brown eyes, because green eyes are recessive. people who have green eyes have homozygous recessive alleles for green eyes (two alleles for green eyes).