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 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 determines
dominant
the trait is called dominant.
The allele that is not expressed
recessive
as a trait is called recessive.
Trait:
brown eyes
All the information in the genes,
both dominant and recessive,
defines an organism’s genotype.
The appearance of an organism is
called its phenotype.
For the trait of brown or blue eye-color in
humans, there are three possibilities:
Genotype
Phenotype
homozygous brown
brown eyes
homozygous blue
blue eyes
heterozygous brown
brown eyes
Because
brown is dominant
and blue is recessive.
Eye-color 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
homozygousheterozygous
brown
brown
homozygous
blue
heterozygous
brown
homozygousheterozygous
brown
blue
heterozygous
brown
heterozygous
brown
heterozygous
homozygous homozygous
blue brown
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.
A
AA
Blood Type
Blood Type
AB
BB
B
When alleles are co-dominant:
The phenotype is
the result of both
alleles
BB
AA
AB
The genotype is
always heterozygous
A species is defined as organisms that
resemble one another, can mate, and
produce offspring that can reproduce.
etc…