 Structural genes: genes that contain the information to make a protein.  Regulatory genes: guide the expression of structural genes, without coding for a protein themselves.  Genotype: the genetic makeup of an individual. Genotype can refer to the entire genetic complement or more narrowly to the alleles present at a specific locus on two homologous chromosomes.  Phenotype: an observable or measurable feature of an organism. Phenotypes can be anatomical, biochemical, or behavioral.

 ABO blood system type: refers to the genetic system for one of the proteins found on the surface of red blood cells. Consists of one gene with three alleles: A, B, and O.  Recessive: in a diploid organism, refers to an allele that must be present in two copies (homozygous) in order to be expressed.  Dominant: in a diploid organism, an allele that is expressed when present on only one of a pair of homologous chromosomes.  Co-dominant: in a diploid organism, two different alleles of a gene that are both expressed in a heterozygous individual.

GenotypePhenotype HomozygousAAType A BBType B OOType O HeterozygousAOType A BOType B ABType AB

A complex interaction between genes, environments, and phenotypes.

 Blending inheritance: discredited 19 th century idea that genetic factors from the parents averaged-out or blended together when they were passed on to offspring.  Particulate inheritance: the concept of heredity based on the transmission of genes (alleles ) according to Mendelian principles.

 Heredity characteristics are controlled by particulate unit factors that exist in pairs in individuals.  When an individual has two different unit factors responsible for a characteristic, only one is expressed and is said to be dominant to the other, which is said to be recessive.

 During the formation of gametes, the paired unit factors separate, or segregate, randomly so that each sex cell receives one or the other with equal likelihood.  Mendel’s law of segregation: the two alleles of a gene found on each of a pair of chromosomes segregate independently of one another into sex cells.  During gamete formation, segregating pairs of unit factors assort independently of each other.  Mendel’s law of independent assortment: genes found on different chromosomes are sorted into sex cells independently of one another.

 Point mutation: a change in the base sequence of a gene that results from the change on a single base to a different base.  Autosomal recessive disease: a disease caused by a recessive allele; one copy of the allele must be inherited from each parent for the disease to develop.

 Sickle cell disease: an autosomal recessive disease caused by a point mutation in an allele that codes for one of the polypeptide chains of the hemoglobin protein.

 Insertion mutation: a change in the base sequence of a gene that results from the addition of one or more base pairs in the DNA.  Deletion mutation: a change in the base sequence of a gene that results from the loss of one or more base pairs in the DNA.  Trinucleotide repeat diseases: a family of autosomal dominant diseases that is caused by the insertion of multiple copies of a three-base pair sequence (CAG) that, which codes for the amino acid glutamine. Typically, the more copies inserted into the gene, the more serious the disease.  Ex. Huntington disease

 X-linked disorders: genetic conditions that result from mutations to genes on the X chromosome. They are almost always expressed in males, who have only one copy of the X chromosome; in females, the second X chromosome containing the normally functioning allele protects them from developing X-linked disorders.

 Polygenic traits: phenotypic traits that result from the combined action of more than one gene, most complex traits are polygenic.  Heritability: the proportion of total phenotypic variability observed for a given trait that can be ascribed to genetic factors. Variability caused by genetics Variability caused by genetics + Variability caused by the environment