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Transcript
Mrs. Keadle JH Science Name__________________________________ period _____ date assigned_____________ date due ______________ date returned _____________ Human Traits Lab Introduction Follow the instructions on the power point to complete this activity. Trait 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 widow’s peak or straight hairline bent or straight pinkies cleft or no cleft chin dominant TOTALS recessive 1 Human Traits Lab Mrs. Keadle JH Science Class Data Class Data # of students in class exhibiting the trait Trait # of students in class exhibiting the trait Trait dimples no dimples straight thumbs bent thumbs rolling tongue non-rolling tongue unattached earlobes attached earlobes widow’s peak straight hairline bent pinky fingers straight pinky fingers cleft chin no cleft chin Create a bar graph using the class data. 24 Number of Students with the Trait (by twos) 22 20 18 16 14 12 10 8 6 4 2 no cleft chin cleft chin straight pinky fingers bent pinky fingers straight hairline widow’s peak attached earlobes unattached earlobes non-rolling tongue rolling tongue curved thumb straight thumbs no dimples dimples 0 Dominant and Recessive Human Traits 2 Human Traits Lab Mrs. Keadle JH Science 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 handedness (R) dominant expression symbol right handed hair line (W) widow’s peak straight hairline ear lobes (F) free (unattached) attached hand folding (L) left thumb on top right thumb on top chin features (C) cleft chin no cleft toes (T) second toe longer than big toe second toe shorter than big toe R recessive expression symbol left handed r 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 Human Traits Lab Mrs. Keadle JH Science 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 widow’s peak straight hairline attached ear lobe free earlobe right thumb on top left thumb on top cleft chin 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 trait. 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 trait. 4 Human Traits Lab Mrs. Keadle 56 The ability to roll your tongue is an inherited trait. 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? JH Science 58 Different forms of a gene are called A mutations B alleles A The ability to tongue roll is a rare trait. C chromosomes B The ability to tongue roll is a recessive trait. D phenotype C The ability to tongue roll is a dominant trait. D The ability to tongue roll is a submissive trait. 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 Human Traits Lab