Human Mendelian Traits

By Bryan Greene,2014-07-02 14:46
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Human Mendelian Traits

    Name: ________________________________ Date ________ Class period: Page | 1

    Human Mendelian Traits

    Mendelian Traits are those traits which follow Mendel’s rules of only 2 possible versions (1 dominant, 1

    recessive). There are many examples of this in humans.

1. Use the chart below to determine your phenotype (appearance) and possible genotypes (a pair of

    alleles). Since you cannot do a genetic test right now, if you have the dominant phenotype, you

    should include both the homozygous and heterozygous genotypessee the examples on Tongue

    Rolling on the first row.

    Trait Possible alleles Your Phenotype Your Genotype(s)

    Tongue Able to roll (R) Ex., able to roll RR (homozygous) or Rr Rolling Unable to roll (r) (heterozygous)

Freckles Have freckles (F)

    No freckles (f)

    Widow’s Widow’s peak (W)

    peak Straight (w)

    Earlobe Free hanging (A)

    Attached (a)

    Cleft chin Have cleft (C)

    No cleft (c)

    Thumb Hitchhiker’s (H)

    Straight (h)

    Dimples Dimples (D)

     No dimples (d)

    Interlocking Left thumb on top (L)

    fingers Right thumb on top (l)


    hands are


2. Did you have mostly dominant or recessive traits? ___________________

    3. Compare your findings with other students.

    a. For which trait where most students dominant?

    b. For which trait where most students recessive?

Name: ________________________________ Date ________

    Class period: Page | 2

    4. First complete the Punnett Square on the right using your own genotype for each trait. If you

    have both heterozygous and homozygous genotypes for having a dominant trait, choose one to

    use. The other person’s genotype is provided. After completing the Punnett Square, identify

    possible phenotypes of offspring and the probability of each phenotype in percentage.

a) Freckle genotypes: Yours ____ & the other person’s Ff

    List possible Phenotypes % (Probability of inheritance)

b) Tongue rolling genotypes: Yours ____ & the other person’s rr

    List possible Phenotypes % (Probability of inheritance)

c) Dimple genotypes: Yours ____ & the other person’s DD

    List possible Phenotypes % (Probability of inheritance)

d) Widow’s peak genotypes: Yours ____ & the other person’s Ww

    List possible Phenotypes % (Probability of inheritance)

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