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Across 3. A test made in early pregnancy to detect congenital abnormalities in the fetus 6. The failure of homologous chromosomes to separate normally during nuclear division. 7. A threadlike structure of nucleic acids and protein found in the nucleus of most living cells 10. an indivicual that has one copy of a recessive allele that causes a genetic disease in individual that are homozygous for this allele 11. Alleles of an organism 14. The sampling of amniotic fluid using a hollow needle inserted into the uterus, to screen for developmental abnormalities in a fetus. 16. n allele that produces the same phenotype whether its paired allele is identical or different. 18. Showing a degree of similarity (e.g. in position, structure, function or characteristics) that may indicate a common origin. 19. A unit of heredity that is transferred from a parent to offspring 20. Having a single set of unpaired chromosomes 21. Containing two complete sets of chromosomes, one from each parent. 22. One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome. 23. Any of a group of basic proteins found in chromatin

Down 1. A type of point mutation in which a single nucleotide is substituted with (or exchanged for) a different nucleotide that may result in an altered sequence of amino acid during translation, which may render the newly synthesized protein ineffective. 2. the particular position on homologous chromosomes of a gene 3. the phenotype 4. having two different alleles of a gene 5. pairs of alleles that both affect the phenotype when present in a heterozygote 8. The haploid set of chromosomes of an organism 9. testing a suspected heterozygote by crossing it with a known homozygous recessive 12. The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. 13. The number and visual appearance of the chromosomes in the cell nuclei of an organism or species. 15. having 2 identical alleles of a gene 17. An organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct.