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| Heredity | The transmission of traits from one generation to the next, however the offspring are not identical to their parents or siblings due to variation. |
| Genetics | The scientific study of heredity and hereditary variation. |
| Gametes | The vehicles that transmit genes from one generation to the next. These genes are produced during DNA replication so they can be passed on from parents to offspring. |
| Locus | A gene's specific location along the length of a chromosome. |
| Asexual Reproduction | A single individual is the sole parent and passes copies of all its genes to its offspring. DNA is copied and allocated equally to two daughter cells with genomes that are almost identical to that of the parent. |
| Sexual Reproduction | Two parents give rise to offsprin thta have unique combinations of genes inherited from the two parents. The offsprin produced from this vary genetically from their siblings and parents. |
| Karyotype | The ordered display of chromosomes that are arranged in pairs, starting witht the longest chromosome. |
| Sex Chromosomes | The chromosomes that determine an individual's sex, the X and Y chromosomes. All the other chromosomes are autosomes. |
| Diploid Cell | Any cell with two chromosome sets has a diploid number of chromosomes, abbreviated 2n. |
| Haploid Cell | Any cell that has a single set of chromosomes. These are gametes (sperm and eggs). This haploid number of chromosomes is abbreviated n. |
| Fertilization | A haploid sperm from the father fuses with a haploid egg from the mother resulting in the fusion of their nuclei. |
| Zygote | The resulting egg after fertilization. It is diploid because it contains two haploid sets of chromosomes with genes from the maternal and paternal family lines. |
| Meiosis | A modified type of cell division for sexually reproducing organisms. This reduces the number of sets of chromosomes from 2 to 1 in the gametes which counteracts the doubling that occurs during fertilization. |
| Alternation of Generations | This is a type of life cycle exhibited by plants and some algae where both diploid and haploid stages are multicellular. The diploid stage is the sporophyte and the haploid stage is the gametophyte. |
| Prophase 1 | Chromosomes begin to condense and homologs loosely pair along their lengths. Crossing over occurs and synapsis ends. Also, the centrosome moves, spindles form, and the nuclear envelope breaks down. |
| Metaphase 1 | Pairs of homologs are arranged along the metaphase plate with one chromosome in each pair facing each pole. |
| Homologs | A pair of chromosomes of the same length, centromere positions, and staining pattern that possess genes for the same characters at corresponding loci. |
| Anaphase 1 | Homologs separate because proteins responsible for sister chromatid cohesion breaksdown. Homologs move toward opposite poles. |
| Telophase 1 | Each half of the cell has a complete haploid set of replicated chromosomes. Each chromosome is composed of 2 sister chromatids. In animal cells, a cleavage furrow forms and a cell plate forms in plant cells. |
| Cytokinesis | The division of the cytomplasm that usually occurs simultaneously with telophase 1, forming 2 haploid daughter cells. |
| Prophase 2 | A spindle apparatus forms and chromosomes, each still composed of two chromatids, begin to move toward the metaphase 2 plate. |
| Metaphase 2 | Chromosomes are positioned on the metaphase plate. Chromosomes are not genetically identical because of crossing over. |
| Anaphase 2 | Chromatids separate because of the breakdown of proteins holding them together. These chromatids move toward opposite poles. |
| Telophase 2 and Cytokinesis | Nuclei form, the chromosomes begin to decondense, and cytokinesis occurs resulting in 4 daughter cells. |
| Synapsis | Replicated homologs pair up and become physically connected along their lengths by a zipper-like protein structure, the synaptonemal complex. |
| Crossing Over | The reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis. |
| Law of Independent Assortment | States that each pair of alleles segregates independently of each other pair of alleles during gamete formation. |
| Recombinant Chromosomes | Chromosomes produced from crossing over. These are individual chromosomes that carry genes derived from two different parents. |
| Character | A heritable feature that varies among individuals, such as flower color. |
| Trait | Each variant for a character, such as purple or white flower colors. |
| Complete Dominance | F1 offspring always look like one of the two parental varieties because of this. The phenotypes of the heterozygote and the dominant homozygote are indistinguishable. |
| Incomplete Dominance | Neither allele is completely dominant, so the F1 hybrids have a phenotype somewhere between those of the two parental varieties. Ex. red and white make pink |
| Codominance | The two alleles both affect the phenotype in separate, distinguishable ways. |
| True-breeding | Referring to plants that produce offspring of the same variety when they self-pollinate. |
| Hybridization | The mating, or crossing, of two true-breeding varieties. |
| Law of Segregation | The two alleles for a heritable character segregate during gamete formation and end up in different gametes. Thus, an egg or a sperm gets only one of the two alleles that are present in the somatic cells of the organism making the gamete. |
| Dominant Allele | Determines the organism's appearance. |
| Recessive Allele | Has no noticeable effect on the organism's appearance. |
| Pedigree | Information about a family's history for a particular trait organized in a family tree describing the traits of parents and children across the generations. |
| Carriers | Heterozygotes that are phenotypically normal with regard to the disorder, but they can still transmit the recessive allele to their offspring. |
