Organisms have thousands of genes, organized into chromosomes, which determine what the animal looks like and what it can do.

In RoboRiot each robot has one gene with two “alleles”. Each robot contributes one “allele” to

the recycler.

In humans each gene has two alleles. Each parent contributes one allele for a trait.

Heredity:An offspring gets one allele related to a trait from each of its parents. The two alleles are responsible for that trait in the offspring.

Alleles

determine trait

When the two alleles in a gene are different for a trait, the gene isheterozygous.

When the two alleles in a gene are the same for a trait, the gene is homozygous.

When an organism has two alleles that are the same for a trait, both determine the trait.

When an organism has two different alleles for a trait, only one trait is expressed.

The allele that is not expressed as a trait is called recessive.

Trait: brown eyes

The allele that determines the trait is called dominant.dominant

recessive

The appearance of an organism is called its phenotype.

All the information in the genes, both dominant and recessive, defines an organism’s genotype.

For the trait of brown or blue eye-color in humans, there are three possibilities:

Genotype Phenotypehomozygous brown

homozygous blue

heterozygous brown Becausebrown is dominant and blue is recessive.

brown eyes

blue eyes

brown eyes

Eye-color Genotype PossibilitiesMother’s Genotype Father’s Genotype Offspring’s Genotype Possibilities

homozygous blue

heterozygous brown

heterozygous brown

heterozygous brown

homozygous brown

homozygous brown

homozygous blue

homozygous blue

homozygous brown

heterozygous brown

heterozygous brown

homozygous blue

heterozygous brown

heterozygous brown

homozygous brown

homozygous blue

homozygous brown

homozygous blue

homozygous brown

The alleles in some genes are neither dominant nor recessive. Both alleles are expressed when the genotype is heterozygous. This is called co-dominance.

Blood Type Blood TypeBlood Type

BBBAAA AB

When alleles are co-dominant:

AB

AA BB

The genotype is always heterozygous

The phenotype is the result of both alleles

AA BB

A species is defined as organisms that resemble one another, can mate, and produce offspring that can reproduce.

etc…