A karyotype is essentially a photograph of a cell's chromosomes taken through a microscope. Researchers set up a karyotype by using chemical solutions to halt a dividing cell in metaphase (when chromosomes are most condensed), then staining the chromosomes with dyes and taking micrograph photos. To display the karyotype, the chromosomes are grouped and numbered by size so the researchers can check for extra chromosomes, missing chromosomes, or other abnormalities. The adjacent image illustrates a normal human karyotype. HeLa cells, descended from the original cervical cancer cells of Henrietta Lacks, are unique in that they can vary widely in chromosome number. Defects in proteins that orchestrate cell division result in descendant cells with too many or too few chromosomes, one of the hallmarks of cancer cells. The karyotype that follows, originally published in 1989, shows all of the chromosomes in a single metaphase HeLa cell. Courtesy of Dr. Thomas Ried, NIH and the Association for Cancer Research/ National Human Genome Research Institute Compare the HeLa cell karyotype with the normal human karyotype, then answer the questions that follow. Courtesy of Dr. Thomas Ried, NIH and the Association for Cancer Research/ National Human Genome Research Institute Including the sex chromosomes, the chromosome number of a normal human cell is enter answer and the chromosome number of this HeLa cell is enter answer . (Hint: Chromosome number is different from total chromosome count.)