Name period date assigned date due date returned. Human Traits Lab. Introduction Follow the instructions on the power point to complete this activity.

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1 Name period date assigned date due date returned Introduction Follow the instructions on the power point to complete this activity. phenotype (which one do you have) dominant or recessive? possible genotype dimples or no dimples straight or curved thumb rolling or nonrolling tongue unattached or attached ear lobes or straight hairline bent or straight pinkies cleft or no cleft chin dominant TOTALS recessive 1

2 dimples no dimples straight thumbs curved thumb rolling tongue non-rolling tongue unattached attached straight hairline bent pinky straight pinky no Number of Students with the (by twos) Mrs. Keadle Class Data Class Data # of students in class exhibiting the trait # of students in class exhibiting the trait dimples straight thumbs rolling tongue unattached bent pinky no dimples bent thumbs non-rolling tongue attached straight hairline straight pinky no Create a bar graph using the class data Dominant and Recessive Human s 2

3 Genes determine traits. An allele is a form of a gene. Each gene occurs in pairs. Each gene may occur in one of two forms, either dominant or recessive alleles. 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 below, 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. Complete the table: trait dominant expression symbol recessive expression symbol handedness (R) right handed R left handed r hair line (W) straight hairline ear lobes (F) free (unattached) attached hand folding (L) left thumb on top right thumb on top chin features (C) no cleft toes (T) second toe longer than big toe second toe shorter than big toe PART 2: Determining the Phenotype Genes come in pairs. 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 below, identify what trait will be seen. The trait that can be seen is called a phenotype. the first example has been done for you. Genotype RR ww FF cc Tt Ll Phenotype (what you can see) the person will be right handed 3

4 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 below with the possible genotypes for each phenotype. The first one has been done for you. Genotype RR or Rr Phenotype (what you can see) the person will be right handed left handed straight hairline attached ear lobe free earlobe right thumb on top left thumb on top no cleft second toe shorter than big toe second toe longer than big toe 55 An offspring inherited a dominant allele from one parent and a recessive allele from the other parent for the same Which of the following is a possible explanation for what will be exhibited by the offspring for that trait? A The offspring will exhibit the recessive trait with the dominant trait being masked. B The offspring will exhibit the dominant trait with the recessive trait being masked. C The offspring will not exhibit that trait because the dominant and recessive traits he received will each mask the other. D The offspring will combine the recessive allele with the dominant allele and exhibit an entirely new 4

5 56 The ability to roll your tongue is an inherited There are more people who can roll their tongues than people who can t roll their tongues. Which of the following could be a correct assumption to explain this? A The ability to tongue roll is a rare B The ability to tongue roll is a recessive 58 Different forms of a gene are called A mutations B alleles C chromosomes D phenotype C The ability to tongue roll is a dominant D The ability to tongue roll is a submissive 57 Why does a person who inherits an allele for curly hair and an allele for straight hair have curly hair? A The allele for curly hair is recessive. B The allele for curly hair is dominant. C The allele for straight hair is dominant. D The allele for curly hair is inherited from both parents. 5