Genetic Vocabulary Genotype: The types of the genes of an organism Genotype: The types of the genes of an organism Phenotype: The observable characteristics of an organism Phenotype: The observable characteristics of an organism

Dominant Gene: A gene which, when present on a chromosome, passes on a certain physical characteristic. Dominant Gene: A gene which, when present on a chromosome, passes on a certain physical characteristic. Recessive Gene: A gene that is inferior to another gene that controls the same trait (the dominant gene). The inferior gene does not get expressed in the presence of a dominant gene. Recessive Gene: A gene that is inferior to another gene that controls the same trait (the dominant gene). The inferior gene does not get expressed in the presence of a dominant gene.

Allele: Location of a gene on a chromosome Allele: Location of a gene on a chromosome Homozygous: The state of having two identical alleles of a particular gene (eg AA, aa). Homozygous: The state of having two identical alleles of a particular gene (eg AA, aa). Heterozygous: The state of having two different alleles of a particular gene (eg Aa) Heterozygous: The state of having two different alleles of a particular gene (eg Aa)

The Fundamental Question What is the relationship between genes (genotype) and observable characteristics (phenotype)? The answer? Phenotype = Genotype + Environment.

Genes and Environment Determine Characters Genetically identical hydrangeas growing in soils of different acidity (different environments). The phenotype = genotype + environment principle applies equally to human traits.

Genes, Alleles, and Chromosomes

Consistency is Good Characters investigated by Mendel No matter what the character, Mendel observed a 3:1 ratio of characters in the F 2.

Monohybrid Crosses Yielded Consistent Results Therefore, the Principle of Segregation indeed is a general principle of genetics.

What Works for Peas Also Works for Humans An albino woman In the cross Aa x Aa, where A is a dominant allele for wild type (standard) pigmentation and a is a recessive allele for no pigmentation (albinism), ¾ of offspring will be wild type and ¼ will be albino.

Are Different Characters Like Color and Shape Inherited Together or Inherited Independently? Mendel performed dihybrid crosses to find out. Mendel’s conclusion: Different characters are inherited independently.

Simple Dominance Inheritance – When one trait is determined by one type of gene. List of Simple Dominance Genes: Tongue RollingBlue vs. Brown Eyes Ear-LobesArm Crossing Hand FoldingPTC Multi-Gene Inheritance – When one trait is determined by many genes. List of Multi-gene Inheritances: HeightSkin pigmentation WeightMetabolism

Incomplete Dominance – two different alleles both possess dominance, resulting in a mixture of the alleles’ traits. Examples: Green EyesWavy Hair Pink Roses Co-Dominance – Two different alleles both possess dominance, but the resulting trait features both phenotypes Examples: Type AB BloodSpots Sample problems: A Brown-eyed man whose mom was blue-eyed marries a woman with blue eyes. What is the probability of have a daughter with blue eyes? What two types of eye color could you cross, that could produce offspring with the 3 types of eye colors? A black dog marries a white dog what are the chances that they will produce a puppy with spots?