Review terms

-Traits: different characteristics

-Heredity: the passing of traits from parents to offspring

-Genetics: the study of how traits are passed from parents to offspring

Dominant and Recessive traits

•  A dominant trait is a genetic factor that masks another genetic factor.

• A recessive trait is a genetic factor that is masked or hidden by the presence of a dominant factor.

Chromosomes & Genes

• Chromosome: a collection of genes grouped together in a threadlike strand of DNA

• Gene: the genetic information for one trait, such as flower color or stem length

Allele

• A version of a gene that controls a trait. 

• Example – trait: flower color (purple or white) Each gene has one allele (version of the gene) that controls flower color that may be passed from parent to offspring. 

Using symbols in genetics

• Dominant alleles are represented using CAPITAL letters

• Recessive alleles are represented using lowercase letters

genotype = genetic makeup

phenotype = physical appearance or visible traits

Genotype

• The gene combination for a trait, represented by a combination of alleles

• For example Tt, tt, TT

• You CANNOT see and organism's genotype

Phenotype

• Organism's physical appearance or its visible traits

• For example the flowers of pea plants can be either purple or white

• You CAN see on organism's phenotype

Homozygous

• -When the two alleles of a gene are EXACTLY the same

• -Homozygous dominant has two CAPITAL letters. (TT, FF, RR, PP)

• -Homozygous recessive has two lowercase letters. (tt, ff, rr, pp)

Heterozygous

• -When the two alleles of a gene are different, one dominant and one recessive

• -One capital, one lowercase

• Tt, Ff, Rr, Pp

homozygous vs heterozygous

• 2 dominant alleles = homozygous dominant AA

• 2 recessive alleles = homozygous recessive bb

• 1 dominant & 1 recessive allele = heterozygous Cc