Term | Definition |
Alleles | different forms of a gene |
Dominant | An allele whose trait always shows up in the organism when it is present. It masks the recessive form of the trait |
Egg | female sex cell (gamete) that contains only 1/2 the normal number of chromosomes |
Sperm | male sex cell (gamete) that contains only 1/2 the normal number of chromosomes |
Fertilization | fusion of a an male and female gamete to produce a zygote |
Gamete | male or female sex cell, sperm or egg, contains only 1/2 the normal number of chromosomes |
Genetics | the study of heredity |
Genotype | combination of genes in an organism |
Heredity | passing on of characteristics from parents to offspring |
Heterozygous | a pair of genes where one is the dominant allele and one is the recessive allele — they're different Dd Rr |
Homozygous | a pair of genes where both are either dominant or recessive alleles--they've the same DD rr |
Hybrid | An organism that has two different alleles for a trait. Hybrids are heterozygous for the trait |
Phenotype | outward appearance of an organism, |
Recessive | A trait that is masked when the dominant allele is present |
Sexual Reproduction | Requires 2 parents - Results in offspring that are genetically different from the parents. |
Trait | characteristic that is inherited; can be either dominant or recessive |
Zygote | diploid cell formed when a sperm fertilizes an egg |
Gene | A unit of DNA that controls the development of a trait. It is located on a chromosome and is inherited from a parent through sexual reproduction. |
Purebred | An organism that has two identical alleles for a trait. Purebreds are homozygous for the trait |
Probability | A number that describes how likely it is that an event will occur. |
Punnett Square | A chart that shows the possible combinations of alleles that result from a genetic cross |
DNA | Deoxyribonucleic acid. A molecule that carries the genetic instructions used in the growth of organisms. |
Chromosome | A strand of DNA that is encoded with genes. Located in the nucleus of eukaryotic cells. |
DNA Replication | A process whereby the original (parent) strands of DNA in the double helix are separated and each one is copied to produce 2 new (daughter) strands |
Asexual reproduction | Requires 1 parent. Results in offspring that are genetically identical to the parent. |
Deoxyribose | The sugar that is found in the backbone of DNA and to which the nitrogenous bases are attached |
Nitrogenous bases | Nitrogen containing molecules that are found in DNA. An organisms genetic code is determined by the order of the bases in its DNA. |
Nucleotides | The building blocks of DNA. Each nucleotide contains 1 nitrogenous base, one sugar (deoxyribose), and one phosphate group. |
Double helix | The shape formed by two parallel lines that twist around each other |
XX | The sex chromosome combination found in females |
XY | The sex chromosome combination found in males |
Incomplete dominance | When the phenotype of the heterozygous genotype is distinct from the phenotypes of the homozygous genotypes. The offspring of a red and white flower might be pink instead of red or white.. |
Mutation | when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene |