| A | B |
|---|
| trait | characteristic of an organism (example: hair color) |
| genetics | the study of heredity |
| self-pollination | transfer of pollen from the male part of a flower to the female part of the same flower |
| cross-pollination | transfer of pollen from the male part of one flower to the female part of a different flower |
| genes | units of heredity; pieces of genetic information on a chromosome |
| dominant genes | strong genes that can mask or overpower weaker ones |
| recessive genes | weaker genes than can be masked by stronger ones |
| hybrid | when an organism has two different genes for a certain trait |
| pure | when an organism has two genes that are the same for a certain trait |
| incomplete dominance | when neither gene in a hybrid gene pair can overpower the other; result is a mixed appearance (example: red flower crossed with a white flower results in all pink offspring) |
| probability | the likelihood that an event may or may not take place; percentage of chance for a certain outcome |
| phenotype | physical characteristic that ends up in the organism (examples: "brown hair" or "blond hair") |
| genotype | the makeup of the two genes that an organism has for a certain trait (examples: BB or Bb or bb) |
| chromosomes | strands of DNA in the nucleus of all cells (hint: normal human body cells have 23 pairs of these); all of an organism's genes are coded on these cell structures |
| meiosis | a special cell division process to make egg or sperm cells that will carry only half the normal number of chromosomes |
| mitosis | regular cell division that creates more cells just like the original (always with the same number of chromosomes); purpose is to create more regular cells for body growth or to replace worn out body cells |
| sex chromosomes | pair number 23 in humans; named either XX or XY |
| DNA | complex molecule that is built like a double spiral staircase; chromosomes are long strands of this molecule |
| replication | the process in which DNA molecules (chromosomes) make exact duplicates of themselves |
| sex-linked trait | characteristic that is passed from parent to child on the X chromosome only (no gene information is found on the Y chromosome) |
| nondisjunction | when chromosomes don't separate properly : the result is often a "trisomy" |
| amniocentesis | test to check on the number of an unborn baby's chromosomes |
| Down Syndrome | a genetic disorder caused by a trisomy on chromosome pair number 21 |
