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.
Heterozygous:an organism that has 2 different alleles for a trait. Homozygous: an organism that has 2 identical alleles for a trait Dominant Allele: an allele whose trait always shows up in the organism when the allele is present, represented by capital letter.elf-fertilization: using the sperms and eggs already had to undergo fertilization. Cross-fertilization: fertilization of one thing by another thing. Purebred Organisms: Hybrids: the offspring of 2 true-breeding varieties.