BABY STEPS:

1. determine the genotypes of the parent organisms.
2. write down your “cross” (mating)
3. draw a p-square.
4. 4. ”
5. determine the possible genotypes of the offspring by filling in the p-square.
6. summarize results (genotypes & phenotypes of offspring)
7. bask in the glow of your accomplishment !

To organize a Punnett square, assign the top of the square for one parent’s genotype and use the left side of the square for the other parent. You will want one row or column per genotype option. The genotype options depend on the potential alleles passed from the parents to the offspring.

The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach in 1905. The diagram is used by biologists to determine the probability of an offspring having a particular genotype.

A Punnett square for a monohybrid cross is divided into four squares, whereas a Punnett square for a dihybrid cross is divided into 16 squares.

Genetic linkage is a phenomenon where two genes exist close to each other on the same chromosome. In addition, when a single trait is determined by multiple genes and the effect of each of these genes is graded, Punnett squares cannot accurately predict the distribution of phenotypes in the offspring.

An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb. Finally, the genotype of an organism with two recessive alleles is called homozygous recessive.

A genotype refers to the genetic characteristics of an organism. A phenotype refers to the physical characteristics.

An individual’s phenotype only includes expressed genes. For example, if an individual has one “brown hair” allele and one “blonde hair” allele, and they have brown hair, their phenotype only includes the expressed gene: brown hair.

Figure 1: Inheritance chart detailing how an individual may inherit blue or brown eyes depending on the alleles carried by their parents, with the brown eye color allele being dominant and the blue eye color allele being recessive. Other examples of genotype include: Hair color.

Mendelian traits, such as the presences of freckles, are traits passed down on one gene with dominant and recessive alleles. Non-Mendelian traits, such as hair color, don’t follow the simple pattern of dominant and recessive alleles from one gene.

Phenotype is the physical appearance eg brown hair.

Blue hair does not naturally occur in human hair pigmentation, although the hair of some animals (such as dog coats) is described as blue. Some humans are born with bluish-black hair (also known as “blue black” hair), which is black that has a blue hue under the light.

A phenotype is your version of a trait. Blue eyes vs brown eyes and curly hair vs straight hair are examples of phenotypes. If you have curly hair, your genotype is two curly hair versions of the hair texture gene: one from mom and one from dad. An allele is the term geneticists use to refer to a version of a gene.

It has been long established that curly hair is a dominant trait in Caucasians and straight hair is recessive. However, a single gene has yet to be found to be solely responsible for the curly (or straight) hair trait in Caucasians.

Genetics 101 Genes are stored inside chromosomes and determine everything from your blood type to your biological sex to your hair color. For every gene, you have two alleles. One came from your mother and one from your father.