Concepts of Biology

The following is a list of some autosomal human traits that have been attributed to a single gene. Although clearly other genes are involved, the inheritance of each of these phenotypic traits acts as if it were governed by a single gene. First, indicate your expression of the trait (i.e., circle the appropriate phenotype). Then, indicate if you exhibit the dominant or recessive trait (D or R?). Finally, using any letters/symbols you want, write your genotype for the trait (hint: if you show the recessive trait, your genotype will be homozygous recessive (i.e., "aa"). If you exhibit the dominant trait your genotype could either be homozygous dominant (i.e., "AA") or heterozygous (i.e., "Aa"). A shorthand symbol for this is "A_"). How could you distinguish between these possibilities?

Trait	Phenotype	Dominant or recessive phenotype?	Genotype
Tongue Rolling (Dominant)	roll/not roll
Widow's Peak (D) - just like Eddie Munster	yes/no
Wet ear wax (D) - stick your finger in to check	wet/dry
L/R interlocking finger (D) - without thinking, clasp your hands together, is the right thumb over the left, or vice versa?	L/R or R/L
Attached earlobes (D) - ask a neighbor or check out the mirror	yes/no
Hitchhiker Thumb (D) - does it bend back at a 90◦ angle	yes/no
PTC tasting (D) - I'll have some test paper in class	yes/no
Chin fissure (D) - like actor Michael Douglas	yes/no
Darwin tubercle (D) - little bump on the inside of the ear	yes/no
S-methylthioester detection (Recessive) - can you smell asparagus odor in urine?	yes/no
Pigmented iris (D) - any color but blue	yes/no
Freckles (D)	yes/no
Polydactyl (D) - more than five fingers and/or toes	yes/no
Dimples (D) - cute!	yes/no
Wooly hair (R)	yes/no
Long eyelashes (> 1cm; D)	yes/no
Short big toe (D) - the big toe is shorter than your second one	yes/no