Term | Definition |
heredity | the passing of physical characteristics from parents to offspring |
trait | each different form of a characteristic such as stem height or seed color |
genetics | the scientific study of heredity |
fertilization | when egg and sperm join and a new organism begins to form |
purebred | offspring of many generations that have the same trait |
gene | factors that control a trait |
alleles | different forms of a gene; for example, the gene that controls the stem height in peas has one allele for tall stems, another allele for short stems |
dominant allele | the trait always shows up in the organism when it is present |
recessive allele | the trait is hidden whenever the dominant allele is present |
hybrid | one of these has two different alleles for a trait; for example, plants are tall because the dominant allele for tall stems masks the recessive allele for short stems. |
probability | a number that describes how likely it is that an event will occur |
Punnett square | a chart that shows all the possible combinations of alleles that come from a genetic cross |
phenotype | an organism's appearance or physical traits |
genotype | an organism's genetic makeup or allele combinations |
homozygous | an organism that has two identical alleles for a trait, for example SS or ss |
heterozygous | having two different alleles for a trait, for example Ss |
codominance | a condition in which neither of two alleles in a gene is dominant or recessive |
chromosome theory of inheritance | according to this, genes are carried from parents to offspring on chromosomes |
chromosomes | made up of many genes joined together like beads on a string |
meiosis | chromosome pairs separate and are distributed to two different cells. the resulting cells have only half as many chromosomes as other cells in the organism |
genes contain __________ | the code that determines the structure of a protein |
nitrogen bases | the order of these along a gene forms a genetic code that specifies what kind of protein will be produced |
mutation | can cause a cell to produce an incorrect protein during protein synthesis; for example, changing the order of nitrogen bases on a chromosome on a gene |
messenger RNA | during protein synthesis, it copies the coded messages from the DNA in the nucleus and carries this message to the ribosome in the cytoplasm |
transfer RNA | carries amino acids to the ribosome and adds them to the growing protein |