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Across 1. visible, observable trait of an organism that masks a recessive form of the trait 5. hidden trait of an organism that is masked by a dominant trait 7. passing on of characteristics from parents to offspring 8. random error or change in the DNA sequence that may affect whole chromosomes or just one gene 9. in DNA, the two twisted, ladder-shaped nucleotide strands held together by hydrogen bonds between the bases 11. process in which the two strands of the double helix separate and bases pair with free nucleotides to form two molecules of DNA, each identical to the original molecule 15. graphic representation showing patterns of inheritance in a family or breeding group 16. equal expression of both alleles 19. absence of a chromosome 20. presence of more than two alleles for a given genetic trait in a species 21. the RNA that composes ribosomes 22. delivers amino acids to the ribosome for protein synthesis 27. major source of genetic variation resulting from crossing over or random assortment 29. structures having a common evolutionary origin 32. Mendelian principle explaining the disappearance of a specific trait in the F1 generation and its reappearance in the F2 generation 35. error in the DNA sequence that affects only a single base pair 36. cell division in which one diploid (2n) cell produces four haploid (n) cells called sex cells 39. reproductive pattern in which haploid gametes fuse to produce a diploid zygote, which then develops by mitosis into a new organism 40. process in which the order of bases in mRNA codes for the order of amino acids in protein 42. a cell of an organism that has half the number of chromosomes (n) 43. male sex cell 45. mating between closely related individuals to produce pure lines 47. fertilization between two organisms to study the inheritance of two different traits 48. offspring produced when two varieties of plants or animals, or closely related species, are mated 50. mutation affecting gene distribution to gametes during meiosis, most commonly by deletions, insertions, inversions, or translocations 51. determination of a given trait, such as skin color or height, produced by the interaction of many genes 52. carries protein synthesis information from DNA to the ribosomes 53. fusion of male and female gametes 54. exchange of genetic material by non-sister chromatids during late prophase I of meiosis, resulting in new combinations of alleles

Down 2. in humans, the 22 matching homologous chromosomes 3. an organism's gene combination 4. branch of biology that studies heredity 6. inherited trait controlled by genes located on the sex chromosomes 10. a cell with two copies of each type of chromosome (2n) 12. inheritance pattern in which the phenotype of the heterozygote is intermediate between those of the two homozygotes 13. in a flower, the process of transfer of pollen grains from the anther to the stigma 14. gene form for each variation of a trait of an organism 17. inherited characteristic 18. Mendelian principle explaining that different traits are inherited independently if on different chromosomes 23. component of DNA or RNA along with a sugar and a phosphate group 24. female sex cell or gamete 25. the process by which enzymes make an RNA copy of a DNA strand 26. having identical alleles for a particular trait 28. in the genetic code, the set of three nitrogen bases representing a specific amino acid 30. failure of homologous chromosomes to separate during meiosis, resulting in gametes with too few or too many chromosomes 31. outward appearance of an organism, regardless if its genes 33. error in the DNA sequence that adds or deletes a single base, causing nearly all amino acids following the mutation to be changed 34. presence of an extra chromosome 37. having nonidentical alleles fro a particular trait 38. in humans, the 23rd pair of chromosomes, which controls the inheritance of sex characteristics and differs males from females 41. male and female sex cells 44. breeding technique used to determine whether an individual is homozygous dominant or heterozygous for a particular trait 46. fertilized egg 49. heterozygous individual that appears phenotypically the same as a homozygous dominant individual, but which has a recessive allele for an undesirable trait