Review - A Gene is a piece of DNA that carries instructions for making a trait. It is passed from parent to offspring. This is called heredity. These chickens have different genes for feather density…

Review - A Chromosome is a large section of DNA containing many genes.

Review - Chromosomes come in pairs, one of each from each parent Review - Chromosomes come in pairs, one of each from each parent. Humans have 23 pairs.

Review - Since you have two of each chromosome, you have two copies of each gene. These copies are called Alleles.

One Allele from Mom + One Allele from Dad = One whole gene One Allele from Mom + One Allele from Dad = One whole gene! Each allele is represented by a letter, so if hair color is represented by the letter H… One hair color Allele from Mom H One hair color Allele from Dad H A complete hair color gene for you! HH

For each trait, there is a Dominant Allele and a Recessive Allele For each trait, there is a Dominant Allele and a Recessive Allele. The Dominant Allele will always be expressed if it is there The Recessive Allele can be hidden by the dominant allele. The two alleles code for different forms of the trait. For example….

For hair color, the dominant allele (H) might code for brown hair, and the recessive allele (h) might code for blonde hair. H = Brown Hair h = Blonde Hair

If you have two dominant alleles, you will have the dominant trait If you have two dominant alleles, you will have the dominant trait. HH = If you have two recessive alleles, you will have the recessive trait. hh = But what if you have one of each? Hh or hH = ?

In most cases, the dominant allele will overpower the recessive allele In most cases, the dominant allele will overpower the recessive allele. So, if you have a dominant and a recessive allele, only the dominant trait will show Hh or hH =

The traits that show up are called your phenotype The traits that show up are called your phenotype. Brown hair is a phenotype. Tongue curling is a phenotype. Size is a phenotype.

The alleles that make up your trait are called a genotype The alleles that make up your trait are called a genotype. HH is a genotype. hh is a genotype. Hh is a genotype.

A Heterozygous genotype is one where both alleles are DIFFERENT, for example (Hh A Homozygous genotype is one where both alleles are THE SAME. Homozygous dominant would be (HH), Homozygous recessive would be (hh) )