Human Traits Lab

The characteristics that an organism inherits from its parents are called traits. In humans, traits include the color of a person's hair, skin, and eyes, the blood group, the shape of the nose and lips, and the tendency to be short-sighted or bald. Some of the traits that humans acquire can be modified by the environment, while others cannot.

Traits are usually considered to be dominant or recessive Traits are usually considered to be dominant or recessive. In a dominant trait, only one allele is necessary to see the trait. In a recessive trait, both copies of the allele must be present to see the trait.

Procedure Take a look at the human traits listed on your paper. For each trait, write down which one you express (have). Write whether it is dominant or recessive and a possible genotype.

dimples or no dimples dominant DD or Dd recessive dd

straight or curved thumb dominant SS or Ss recessive ss

rolling or non-rolling tongue dominant RR or Rr recessive rr

unattached or attached earlobes dominant UU or Uu recessive uu

widow’s peak or straight hairline dominant WW or Ww recessive ww

bent or straight pinkies dominant BB or Bb recessive bb

cleft or no cleft chin dominant CC or Cc recessive cc

Procedure 4. Total up how many dominant traits you have 5. Total up how many recessive traits you have

Fill in the table on your paper

Create a bar graph using the class data

Genes determine traits. An allele is a form of a gene Genes determine traits. An allele is a form of a gene. Each gene has at least two alleles. Each allele may occur in one of two forms, either dominant or recessive. Complete the following to practice understanding how scientists work with alleles. Most traits are the result of several genes, but we will practice with some that are thought to be controlled by a single gene.

PART 1: Symbolizing Alleles In the table, several traits are listed PART 1: Symbolizing Alleles In the table, several traits are listed. The two forms of the gene are listed. Scientists use two forms of the same letter to represent the two alleles. A dominant allele is represented by a capital letter. A recessive allele is represented by a lower case letter. If there is a capital letter, it is usually written first. For each trait, use the letter in parenthesis. The first one has been done for you as an example.

PART 1: Symbolizing Alleles

PART 2: Determining the Phenotype Genes have at least two alleles PART 2: Determining the Phenotype Genes have at least two alleles. There are three possible combinations (genotype) of alleles in each pair. If a dominant allele is present, the dominant trait will appear in the organism. In order for a recessive trait to be expressed, both alleles of the gene pair must be recessive. In the table, identify what trait will be seen. The trait that can be seen is called a phenotype. The first example has been done for you.

PART 2: Determining the Phenotype

PART 3: Determining the Genotype The genotype refers to the alleles in the gene pair. There are three possible combinations. If an organism expresses a dominant trait, there are two possible genotypes. If the organism expresses a recessive trait, there is only one genotype possible. Fill in the table with the possible genotypes for each phenotype. The first one has been done for you.

PART 3: Determining the Genotype

complete the multiple choice questions and turn it in.