| A | B |
|---|
| adenine (A) | nitrogen base found in DNA, always pairs with thymine |
| allele | an alternative form of a gene |
| autosomal chromosome (autosome) | a chromosome that is not directly involved in determining the sex of an organism |
| cancer | the disease caused by an uncontrolled division of abnormal cells in a part of the body |
| cell plate | a plate in plant cells that grows between the identical components of the splitting cell and becomes the solid cell wall |
| centromere | the region where two sister chromatids are attached |
| cleavage furrow | a depression in animal cells that forms as the cell begins its division |
| crossing-over | the exchange of genetic material between homologous chromosomes that results in genetic variability |
| cytosine (C) | nitrogen base found in DNA, always pairs with guanine |
| cytokinesis | the final stage of the cell cycle, during which the cytoplasm divides to form two daughter cells |
| DNA helicase | enzyme that breaks the hydrogen bonds that hold the nucleotide bases together |
| DNA polymerase | enzyme that adds complementary nucleotides to each strand of DNA |
| diploid | containing both chromosomes from each homologous pair (2n) |
| gamete | specialized cell used in sexual reproduction; sperm and egg cell |
| gametogenesis | process by which gametes are produced |
| gene | basic physical and functional unit of heredity; specific segment of DNA that influences a particular trait or group of traits |
| genome | an organism's complete genetic makeup, including its entire set of chromosomes |
| guanine (G) | nitrogen base found in DNA, always pairs with cytosine |
| haploid | containing one chromosome from each homologous pair (n) |
| homologous chromosomes (homologs) | a pair of similar chromosomes with the same genes in the same locations |
| interphase | the longest stage of the cell cycle during which the cell grows, replicates its DNA, and prepares to divide |
| meiosis | a type of cell division that produces cells used in sexual reproduction |
| mitosis | the second stage of the cell cycle, during which the nucleus is divided |
| semi-conservative | each copy of DNA contains one newly-replicated strand and one strand from the original molecule |
| sex chromosome | a chromosome that determines an organism's sex (Humans: females=XX and males=XY) |
| sister chromatid | two copies of replicated DNA that make a chromosome |
| spindle fiber | a microtubule that helps separate the chromosomes during mitosis |
| somatic cell | any cell forming the body of an organism; body cell |
| tetrad | the four chromatids formed by the two sister chromatids in each of the two homologous chromosomes during crossing-over |
| thymine (T) | nitrogen base found in DNA, always pairs with adenine |
| zygote | a fertilized egg |
