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Across 4. Male gametes, or reproductive cells; produced in the testicles. 7. A prenatal diagnostic method in which a sample of amniotic fluid is withdrawn and tested to detect chromosomal abnormalities. 8. A dominant gene disorder that results in a gradual deterioration of the central nervous system, causing uncontrollable movements and mental deterioration. 11. Also called trisomy 21 because it is generally caused by an extra twenty-first chromosome or the translocation, or transfer, of part of the twenty-first chromosome onto another chromosome. 13. A disease in which the blood fails to clot properly and therefore is characterized by excessive bleeding; example of a sex-linked recessive trait. 14. A medical procedure for detecting genetic abnormalities before birth in which a small bit of tissue surrounding the embryo is removed and examined microscopically. 15. In any paired set of genes, the gene with greater influence in determining physical characteristics that are physically visible or manifest. 16. The creation of new cells through duplication of chromosomes and division of cells. 18. Describes a genotype consisting of distinct forms of chromosomes for the same gene. 19. A molecular structure, carried on chromosomes, containing genetic information; the basic unit of heredity. 21. The tendency of many developmental processes to unfold in highly predictable ways under a wide range of conditions. 22. In any paired set of genes, the gene that influences or determines physical characteristics only when no dominant gene is present. 24. A reproductive cell (sperm or ovum). 26. A research method for studying the relative contributions of heredity and environment in which the degree of similarity between genetically identical twins is compared with the similarity between fraternal twins. 27. The reproductive cell, or gamete, of the female; the egg cell. 28. The set of traits an individual actually displays during development; reflects the evolving product of genotype and experience. 29. One of several alternative forms of a gene.

Down 1. A research method for studying the relative contributions of heredity and environment in which genetically related children reared apart are compared with genetically unrelated children reared together. 2. A molecule containing hereditary information; has a chemical structure of two chains of polynucleotides arranged in a double helix or spiral. 3. The range of possible phenotypes that an individual with a particular genotype might exhibit in response to the particular sequence of environmental influences he or she experiences. 4. A genetically transmitted condition in which a person’s red blood cells intermittently acquire a curved, sickle shape. The condition sometimes can clog circulation in the small blood vessels. 5. Results from having only one sex chromosome; thus, affected individuals are, by default, female. 6. The scientific study of the relationship between genotype and phenotype, especially with regard to intelligence, personality, and mental health. 9. A disorder of the nervous system that occurs most frequently among people of German or Eastern European Jewish origin. 10. A threadlike, rodshaped structure containing genetic information that is transmitted from parents to children; each human sperm or egg cell contains twenty-three chromosomes, and these determine a person’s inherited characteristics. 12. A complex process by which gametes form; involves duplication and division of reproductive cells and their chromosomes. 17. A genetic condition in which an individual inherits two identical genes at a particular location on a particular chromosome. 20. A prenatal diagnostic method that allows medical personnel and others to view the fetus by projecting high-frequency sound waves through the mother’s womb. 23. The set of genetic traits inherited by an individual. 25. The single new cell formed when a sperm cell attaches itself to the surface of an ovum.