Question

Observing human phenotypes and probability in genetics

Name: _________________________

Purpose

Reinforce concepts of simple genetics by examining the following:

Genotype

Phenotype

Homozygous

Heterozygous

Dominant

Recessive

Materials

Mirror

Objectives

Determine your phenotype for ten different traits.

Determine your possible genotypes for the ten different traits.

Evaluate your uniqueness as an individual.

Part A- Determining your phenotype and genotype

In part “A” you will examine your phenotype, or appearance, and will draw conclusions about your

genotype, the gene combinations that determine appearance. For this exercise let’s use the upper and

lower case of letter “H.” The first one we will do together as an example. The traits we will study have

little significance in making us better or worse persons; they just help make us more interesting!

1.)

Cleft in chin

This trait has been well documented. Absence of a cleft is dominant and presence of a cleft is recessive.

Phenotype _______________

Genotype ________________

Ok, I do not have a cleft so for phenotype I would place in the phenotype blank “no cleft.” My

phenotype contains the dominant gene so my genotype could be “HH” or “Hh.” Remember that you

can have a heterozygous or homozygous dominant individual. However, you can only have a

homozygous recessive individual; “hh.”

2.)

Hairline

A slight dip in the center of the hairline called a widow’s peak is dominant. A straight hairline is

recessive.

Phenotype _______________

Genotype ________________

3.)

Eyelash length

Long eyelashes are dominant and homozygous. Hybrid eyelashes, long eyelashes in the middle and

short on the ends, are heterozygous. Short eyelashes are recessive and homozygous.

Phenotype _______________

Genotype ________________

4.)

Dimples

Dimples are dominant, homozygous or heterozygous. Absence of dimples is recessive and homozygous.

Phenotype _______________

Genotype ________________

5.)

Earlobes

Definite free earlobes are dominant, homozygous or heterozygous. Attached earlobes are recessive,

homozygous.

Phenotype _______________

Genotype ________________

6.)

Freckles on cheeks

Freckles are dominant, may be homozygous or heterozygous. Freckles absent is recessive,

homozygous.

Phenotype _______________

Genotype ________________

7.)

Tongue rolling

The ability to roll the tongue, side edges up, is dominant, may be homozygous or heterozygous.

Phenotype _______________

Genotype ________________

8.)

Interlaced fingers

Fold your hands together, interlacing the fingers. Look at your thumbs. Left over right is dominant.

Right thumb over left is recessive.

Phenotype _______________

Genotype _______________

Answer 1