Transcript Slide 1 - MisterSyracuse.com

Name ___________________________________ Date ____________________ Period ______________
Your Own Pair of Jeans
So you think genetics doesn’t apply to you? So you’re not part of biology you
say? Nothing we learn in this class could possibly apply to you? Well, my little
cabbages, think again! Use this worksheet to examine some common and visible human
phenotypes, and make some hypotheses about your genotypes for those traits! After you finish with the
sheet, take it home to see if parents, uncles, aunts, grandparents, brothers, sisters, dogs, cats, hamsters, fish,
etc. have any of the same traits. Maybe you can make a pedigree for a trait of your choosing! Good luck,
now go forth and do science!
1. When the hairline on the forehead dips down in the middle, it is called a widow’s peak. The gene for this
is dominant to the gene for no widow’s peak.
Your phenotype:
Your genotype:
2. A dimpled or cleft chin is dominant to a smooth chin.
Your phenotype:
Your genotype:
3. The ability to roll the tongue into a U-shape when it is extended beyond the lips is granted by the
presence of a dominant gene.
Your phenotype:
Your genotype:
4. When the hand is laid flat on a smooth surface and the muscles are relaxed, the little finger of some
people will be bent. This is a dominant trait. A straight little finger is caused by a recessive gene.
Your phenotype:
Your genotype:
5. The palmer muscle is located on the underside of the arm, and is connected to the bones of the wrist with
either two or three tendons. When the fist is clenched, these tendons become visible through the skin near
the middle of the underside of your wrist. The presence of two tendons is caused by a dominant gene, while
three tendons is the result of a recessive gene.
Your phenotype:
Your genotype:
6. Free earlobes are dominant over attached earlobes. (you might want to check a mirror or have a friend do
this one…you’ll look rather silly trying to see your own earlobes…)
Your phenotype:
Your genotype:
7. Mid-digital hair present between the first two knuckles of the fingers is a dominant trait. The complete
absence of this hair is a recessive trait.
Your phenotype:
Your genotype:
8. PTC, or phenylthiocarbamide (fee-nal-thee-oh-carb-ah-myed) is a very bitter substance that was
discovered, quite accidentally, by a chemist named Arthur Fox in 1930. He was working with the substance
in the lab, and spilled it. He noted that not all of his labmates could taste the acrid chemical. A prevalent
hypothesis for the existence of this gene is that bitter things, back in the day, were probably poisonous and
shouldn’t be ingested. The practical upshot of this today, is that people who can taste PTC are less likely to
eat some of the more bitter veggies, and are also less likely to smoke. There is a disproportionate number of
people who are non-tasters and who also smoke. The taster gene is incompletely dominant to the non-taster
gene. This means that non-tasters have two recessive alleles, those who taste a little are heterozygous, and
those who taste a lot are homozygous dominant.
Your phenotype:
Your genotype:
9. The thumb, when extended in the “hitchhiking” position, is not perfectly straight. A bend of less than 90
degrees is caused by a recessive gene, while “hitchhiker’s thumb,” a bend of greater than 90 degrees, is
caused by a dominant gene.
Your phenotype:
Your genotype:
10. Red-green colour deficiency is caused by a gene on the X chromosome. If a female is colorblind, she
has two recessive alleles (XbXb), and if a male is colorblind, he has only one X, so only one copy (XbY).
This gene, because it varies based on the sex of the individual, is said to be sex-linked.
Your phenotype:
Your genotype:
Class Data (total number in class __________)
Trait
Hairline
Chin
Tongue
Little Finger
Palmer Muscle
Earlobes
Mid-digital hair
PTC
Thumb
Colour Deficiency
Genotypic Ratio
Phenotypic Ratio