Wavy hair—a person that is homozygous dominant has curly hair. Homozygous

recessive genotype has straight hair. A

person who is heterozygous has

curly hair.

Red-green colorblindness—the gene that codes for colorblindness is located on the x chromosome and is inherited at the same

time as the x chromosome. Females are in luck because the gene is recessive.

Females need two copies of the gene to be colorblind. Males only get one copy of the x chromosome so if they get one copy of the

gene they are colorblind.

Kernel colors of corn—when corn with white kernels is crossed with

corn with blue kernels the offspring will have a mix of white and blue

kernels.

PKU—there are several alleles involved in coding for enzyme that breaks down

phenylalanine. Phenylketonuria (PKU) is a disease in which the one of the alleles is mutated so a person cannot metabolize

phenylalanine. The phenylalanine can build up in the person’s brain cells causing severe

damage.

Skin color—the number of genes that contribute to

skin color in humans is still being studied. There are definitely more than four genes that contribute to

skin color.

AB blood type—B blood type (Genotypes BB or BO) has B antigens on blood cells. A blood type (Genotypes AA or AO) has A antigens on blood cells. AB blood type (Genotype AB) has A and B antigens on blood cells.

Cystic Fibrosis—this is a disease caused by one of several hundred

alleles within the population. The phenotypes from this disease range

widely from susceptibility of bronchitis to sterility.

Eye Color—the general eye color in humans is determined by two

different genes. The eye color can also be affected by several other

genes.

Tay-Sacs Disease—the normal human has homozygous alleles for producing LDL receptors. The LDL receptors help lower cholesterol. The homozygous genotype for not producing LDL receptors would not be able to survive. The heterozygous genotype referred to as Tay-Sacs Disease) has one allele that produces LDL receptors and one allele that does not. A person with this genotype has about half the LDL receptors of a normal person which can lead to high cholesterol levels.

Flower color- when red roses are crossed with white roses the result

is a pink rose.

Chicken Feathers- A black chicken crossed with a white

rooster has offspring with black and white feathers.

Hemophilia- people with hemophilia have blood that does

not clot well. Whenever they have a cut they have excessive bleeding.

This is a recessive trait and the gene for the trait is located on the x

chromosome.