| A | B |
|---|
| blending concept of inheritance | Individuals with two contrasting traits will have offspring with intermediate appearance--red and white parents will have pink offspring flowers |
| particulate theory of inheritance | based on the existence of minute particles, or hereditary units, that we now call genes |
| monohybrid cross | a cross of a single trait with organisms that are hybrid (heterozygous)-Tt |
| locus | a particular location for a gene |
| alleles | alternate forms of a gene |
| dominant allele | will mask the expression of the recessive allele, only need 1 copy for the trait to be expressed |
| recessive allele | will be hidden unless there are two copies of the allele in an individual |
| homozygous | two identical alleles for a particular trait |
| heterozygous | two different alleles for a single trait |
| genotype | alleles an individual has |
| phenotype | the physical appearance (expression) of the genotype |
| dihybrid cross | Organisms are hybrid for two different traits (heterozygous)--example TtGg |
| law of segregation | the two factors for each trait separate during the formation of gametes and each gamete contains only one factor |
| law of independent assortment | each pair of factors segregates (assorts) independently of the other pairs and all possible combinations of factors can occur in gametes |
| Punnett square | diagram used to calculate the results of a cross |
| testcross | a cross used to determine the genotype of an organism with a dominant phenotype by crossing with an individual that is homozygous recessive |
| autosome | any chromosome other than the X and Y (sex chromosomes) |
| autosomal dominant inheritance | a trait in which only one copy of the dominant allele is needed to express the trait, individuals that are homozygous dominant and heterozygous will express the trait (AA or Aa). Both males and females are affected with equal frequency. |
| autosomal recessive inheritance | a trait in which both copies of the gene (alleles) need to be recessive in order for the individual to be affected (aa). Both males and females will be affected with equal frequency. |
| multiple alleles | When a trait is controlled by more than two alleles and exists in several allelic forms in the population. |
| codominance | Alleles are fully expressed in the presence of the other. Example, I(A) and I(B) blood type alleles. Both alleles will be expressed. |
| incomplete dominance | Exhibited when the heterozygote has an intermediate phenotype between that of either (example, heterozygous snapdragon flowers are pink-Rr) |
| incomplete penetrance | The dominant allele does not always determine the phenotype of the individual. In other words, just having the dominant allele does not mean you will full express the gene (polydactyly |
| pleiotropy | This occurs when a single mutant genes affects two or more distinct or seemingly unrelated traits |
| polygenic inheritance | When a trait is governed by two or more sets of alleles and produces a range of phenotypes (a bell curve). Examples include height, skin color and eye color in humans. |
| multifactorial traits | Traits controlled by polygenes subject to environmental influences. |
| X-linked | A trait that comes from a gene on the X chromosome, will only have 1 allele in males. |
| hemizygous | Males are considered this for X-linked traits. |
