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| 12711466862 | Diploid (2n) | Having a chromosome complement consisting of two copies (homologs) of each chromosome. Designated 2n. |  | 0 |
| 12711471057 | Haploid (n) | Having a chromosome complement consisting of just one copy of each chromosome; designated 1n or n. | | 1 |
| 12711474252 | Sister chromatid | Each of a pair of newly replicated chromatids. |  | 2 |
| 12711493260 | Meiosis | Division of a diploid nucleus to produce four haploid daughter cells. The process consists of two successive nuclear divisions with only one cycle of chromosome replication. In meiosis I, homologous chromosomes separate but retain their chromatids. The second division meiosis II, is similar to mitosis, in which chromatids separate. |  | 3 |
| 12711496729 | Gamete | The mature sexual reproductive cell: the egg or the sperm. |  | 4 |
| 12711500372 | Somatic cell | All the cells of the body that are not specialized for reproduction. |  | 5 |
| 12711505224 | Crossing over | Process in which homologous chromosomes exchange portions of their chromatids during meiosis. Increases genetic variety. |  | 6 |
| 12711521654 | Homologous chromosome | A set of one maternal and one paternal chromosome that pair up with each other inside a cell during meiosis. |  | 7 |
| 12711548164 | Zygote | The fertilized egg. The cell created by the union of two gametes, in which the gamete nuclei are fused. The earliest stage of the diploid generation. |  | 8 |
| 12711552234 | Nondisjunction | Failure of sister chromatids to separate in meiosis II or mitosis, or failure of homologous chromosomes to separate in meiosis I. Results in aneuploidy. |  | 9 |
| 12711556684 | Independent assortment | Formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes by the passage according to the laws of probability of one of each diploid pair of homologous chromosomes into each gamete independently of each other pair. |  | 10 |
| 12711564351 | Genetics | The study of heredity and the variation of inherited characteristics. |  | 11 |
| 12711568486 | Genotype | An exact description of the genetic constitution of an individual, either with respect to a single trait or with respect to a larger set of traits. |  | 12 |
| 12711574413 | Phenotype | The observable properties of an individual resulting from both genetic and environmental factors. | | 13 |
| 12711580968 | Law of Segregation | In genetics, the separation of alleles, or of homologous chromosomes, from each other during meiosis so that each of the haploid daughter nuclei produced contains one or the other member of the pair found in the diploid parent cell, but never both. This principle was articulated by Mendel as his first law. |  | 14 |
| 12711586532 | Law of Independent Assortment | During meiosis, the random separation of genes carried on nonhomologous chromosomes into gametes so that inheritance of these genes is random. This principle was articulated by Mendel as his second law. | | 15 |
| 12711590030 | Dominant | In genetics, the ability of one allelic form of a gene to determine the phenotype of a heterozygous individual in which the homologous chromosomes carry both it and a different (recessive) allele. |  | 16 |
| 12711593520 | Recessive | In genetics, an allele that does not determine phenotype in the presence of a dominant allele. |  | 17 |
| 12711598648 | Monohybrid cross | A mating in which the parents differ with respect to the alleles of only one locus of interest. |  | 18 |
| 12711603122 | Dihybrid cross | A mating in which the parents differ with respect to the alleles of two loci of interest. |  | 19 |
| 12713155634 | Homozygous | In diploid organisms, having identical alleles of a given gene on both homologous chromosomes. An individual may be a homozygote with respect to one gene and a heterozygote with respect to another. |  | 20 |
| 12713159834 | Heterozygous | In diploid organisms, having different alleles of a given gene on the pair of homologs carrying that gene. |  | 21 |
| 12713161906 | Gene | A unit of heredity. Used here as the unit of genetic function which carries the information for a polypeptide or RNA. |  | 22 |
| 12713164221 | Allele | A specific form of a gene at a given locus on a chromosome, among multiple possible forms. |  | 23 |
| 12713167343 | Test cross | Mating of a dominant-phenotype individual (who may be either heterozygous or homozygous) with a homozygous-recessive individual; used to determine whether the test organism is homozygous dominant or heterozygous. | | 24 |
| 12713172662 | Probability | A numerical quantity that expresses the likelihood of an event occurring on a scale from 0 (no chance of the event) to 1 (certainty of the event). |  | 25 |
| 12713175924 | Genotypic ratio | Pattern of offspring distribution according to genotype (i.e. the genetic constitution determining the phenotype of an organism) |  | 26 |
| 12713181314 | Phenotypic ratio | Pattern of offspring distribution according to phenotype (i.e. observable characteristic) |  | 27 |
| 12713187874 | Pedigree | The pattern of transmission of a genetic trait within a family. |  | 28 |
| 12713190163 | Sex-linked traits | A trait that is controlled by a gene or an allele located on the sex chromosome. |  | 29 |
| 12713200748 | Incomplete dominance | Condition in which the heterozygous phenotype is intermediate between the two homozygous phenotypes. |  | 30 |
| 12713202076 | Non-nuclear inheritance | Extra nuclear genes that are present in mitochondria and chloroplasts and can reproduce by themselves and pass on their genes to resulting organelles. |  | 31 |
