Organisms have thousands of genes, organized into chromosomes, which determine what the animal looks like and what it can do. Be sure to make the point that both plants and animals have chromosome.

In RoboRiot each robot has one gene with two “alleles” In RoboRiot each robot has one gene with two “alleles”. Each robot contributes one “allele” to the recycler. Explain that since the robots have only two alleles, the number of variations is limited.

In humans each gene has two alleles In humans each gene has two alleles. Each parent contributes one allele for a trait. Whereas Robot have only two alleles, humans have many 46 chromosomes each having with many genes. You may want to ask students if they know about the Human Genome project and how each gene is being mapped.

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 If students have learned about meiosis, they will be familiar with this concept. If they have not, it is important the help them understand that each parent contributes ½ of the offspring’s chromosomes. determine trait

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

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. The allele that determines the trait is called dominant. dominant Trait: brown eyes The allele that is not expressed as a trait is called recessive. 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. The appearance of an organism is called its phenotype.

brown is dominant and blue is recessive. For the trait of brown or blue eye-color in humans, there are three possibilities: Genotype Phenotype homozygous brown homozygous blue heterozygous brown brown eyes blue eyes brown eyes Because brown is dominant and blue is recessive.

Eye-color Genotype Possibilities Offspring’s Genotype Possibilities Mother’s Genotype Father’s Genotype Offspring’s Genotype Possibilities homozygous brown homozygous brown homozygous brown homozygous blue homozygous blue homozygous blue homozygous brown heterozygous brown homozygous brown heterozygous brown homozygous blue heterozygous brown homozygous blue heterozygous brown heterozygous brown heterozygous brown homozygous brown homozygous blue heterozygous brown

The alleles in some genes are neither dominant nor recessive 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 Type Blood Type A A A B B B A B

When alleles are co-dominant: The phenotype is the result of both alleles The genotype is always heterozygous AA AA BB BB AB

A species is defined as organisms that resemble one another, can mate, and produce offspring that can reproduce. You may want to tell students that while a horse and a donkey can mate, their offspring, called a mule, is sterile. etc…