Download Human Traits Lab

Human Traits Lab
Purpose:
 To determine personal phenotypes and genotypes for some observable traits
 To determine the frequencies (%) of dominant and recessive traits in a population
Introduction:
Heredity is the passing on of traits, or characteristics, from parent to offspring. The units of heredity
are called genes. Genes are found on the chromosome in a cell and come in alternate forms called alleles (ex
gene for eye color can have the alleles for green, blue, brown, etc.) The combinations of genes and their alleles
for eachorganism’s trait occur by chance and are inherited from the organism’s parents. In many cases, there
are two alleles for a gene, the dominant and recessive allele. Sometimes organisms have two of the same alleles
and are called homozygous dominant or homozygous recessive. Sometimes organism’s have both the recessive
and dominant alleles and said to be heterozygous for that particular gene. The dominant alleles code for the
traits that show up in a higher proportion within heterozygous organisms. They are written as capital letters.
Recessive alleles code for traits that show up in a lower proportion in heterozygous organisms. They are written
as lowercase letters. This genetic makeup or allele combination of an individual is known as its genotype. The
observable physical characteristics of an individual that are the result of its genotype are known as its
phenotype.
Your Phenotype/Genotype # of Recessive # of Dominant
Frequency of
Traits
in class
in class
Recessive
Attached ear lobe. (ee)
Unattached ear lobe.
Blue eyes. (bb)
Non blue eyes.
Widows peak.
Non widows peak. (ww)
Tongue roller.
Non tongue roller. (rr)
Bent pinkie.
Straight pinkie. (pp)
Hair on mid joints.
No hair on mid joints. (hh)
Red hair. (nn)
Any other color of hair.
Curly hair (CC)
Wavy hair (CS)
straight hair (SS)
PTC taster.
Non PTC taster. (aa)
Cleft chin. (cc)
Non cleft chin.
Almond eyes.
Round eyes. (aa)
Eyes straight.
Eyes slanted. (ss)
Bushy eyebrows.
Fine eyebrows. (bb)
Connected eyebrow. (cc)
Non-connected eyebrow.
Freckles.
No freckles. (ff)
Dimples.
No dimples. (dd)
Hitchhiker's thumb. (hh)
Non hitchhiker's thumb.
Cross right thumb over
left (tt)
Cross left thumb over
right.
Right handed.
Left handed. (hh)
Discussion:
1) If a man does not have Hitchhiker’s thumb, what are the two possible genotypes?
2) If a man is homozygous for Hitchhiker’s thumb and marries a woman with homozygous dominant alleles,
what is the probability of them having children with Hitchhiker’s thumb?
3) Is anyone dominant for every trait? Is anyone recessive for every trait? If not, what does this show
about dominance and recessiveness of traits in people?
4) What is the ratio of tongue rollers to non-tongue rollers in the class? What is the frequency (%) of
tongue rollers in the class?
5) What is the ratio of dimples to non-dimples in the class? What is the frequency (%) of dimpled students
in the class?
6) What is the probability of having both of these traits (tongue-rolling and dimples)? To determine this,
multiply the percent of tongue rollers times the percent of those with dimples. Remember you cannot
multiply %…you must make it a decimal first. This will give you the percent frequency of someone having
both traits.
9) How does the ethnic make-up of this class affect this lab?