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.
A dominant allele can show with only one copy present (B) and recessive needs two alleles present (bb) to show. Remembering that B = dominant, b = recessive... 1. 'Homo' = same. A homozygous trait means the alleles are the same (bb or BB) 2. heterozygous dominant trait would be composed of two different alleles, and since it's dominant those alleles would be 'Bb' 4. A homozygous recessive trait would have the same alleles but they would be recessive, so a homozygous recessive trait would be 'bb'. Hope that made some sort of sense!