1. I can…
take an inventory of my observable traits and
compare them to the observable traits of family
members.
differentiate between gene/allele,
dominant/recessive traits, phenotype/genotype,
homozygous/heterozygous
2. There are over 200 traits that are transmitted from generation to
generation in humans. Traits are physical characteristics that you
inherit from your parents.
An alternate form of a gene for a trait is called an allele.
One of the human traits we are going to look at is Widow’s Peak v. straight
hairline.
Alleles are represented by letters and may be dominant (A) or recessive (a)
3. Genotype
The genetic make-up of an organism.
Represented by two alleles (one from mom, one from dad)
Homozygous (BB, bb) OR Heterozygous (Bb)
Phenotype
The outward, physical appearance of an organism. (brown
hair, left-handed, freckles)
If the dominant allele is present we will see the dominant
trait (BB, Bb). We only see the recessive trait expressed in
the absence of a dominant allele (bb).
4.
5. Look at each trait and determine your
phenotype (outward appearance)
Identify if you exhibit the dominant or
recessive version of the trait
DISCLAIMER-We are doing these for fun, they
do not all follow a simple inheritance pattern
as we are suggesting.
6. Male (XY) Female (XX)
Your sex is determined by whether you get an X or Y chromosome
from your father. Everyone receives an X from their mother.
15. Morton’s Toe, also called “long toe” is the common term for the
second toe extending past the big toe.
Morton’s Toe (T) is dominant over a longer big toe.
16. If you cannot see the
number inside the
circles, you may be
colorblind.
Normal (N) is
dominant over
colorblindness.
18. PTC tasting (P) is
dominant.
75% of individuals can
taste the bitter flavor
of PTC.
Non-tasting is
recessive.
25% of individuals find
the paper tasteless.
PTC is a bitter flavor compound that often causes people to
dislike certain foods, such as broccoli, coffee, or beer.
19.
20. 1. Is it true that dominant phenotypes are always the most
common in the population?
2. Is it possible to determine the genotype of a person showing
a dominant phenotype?
3. Is it possible to determine the genotype of a person showing
a recessive phenotype?
4. People comment that “Joe” looks so much like his uncle. Did
Joe inherit his good looks from his uncle?
21. 5. Given the genotypes above, would the dominant or recessive
phenotypes be expressed?
6. What is key in determining this?
7. Which are referred to as homozygous? As heterozygous?
8. What is key to determining “zygousness”? (my word!)
a.AA b. Gg c. KK d. nn e. Rr f. dd
22. Tall (T) is dominant over short.
Yellow (Y) is dominant over green peas.
Purple (P) is dominant over white flowers.
Round (R) is dominant over wrinkled.
9. What is/are the possible genotype(s) for…
10. What is the phenotype for…
Editor's Notes
Traits are observable characteristics that are passed down from parent to child. An individual will have many traits they share in common with others. In fact, about 99.8% of your genetic information is the same as your six billion or so fellow humans on Earth. It is the final 0.2% that makes you special.
The size and appearance of the lobes are also inherited traits!
Approximately 55% of people place their left thumb on top, 44% place their right thumb on top and 1% has no preference.
Colorblindness is due to a recessive allele located on the X chromosome. Women have two X chromosomes, one of which usually carries the allele for normal color vision; therefore, few women are colorblind. Men only have one X chromosome, so if they carry the allele for colorblindness, they will exhibit this trait. Thus, colorblindness is seen more frequently in men than in women.
In the 1930s at DuPont it was accidently discovered that taste is genetically-based. Arthur Fox had made some phenylthiocarbamide (PTC) and some of the dust had blown into the air. The dust did not bother Fox at all, but his partner, Noller, complained that the dust had a very bitter taste. The two men found it interesting that they could not both taste the PTC, sparking the interest of scientists. The inability to taste PTC was further studied at the Carnegie Department of Genetics by Albert Blakeslee, and it was discovered that the inability to taste PTC is a recessive trait that can be found in humans.
Approximately 75% of people can taste PTC, but it is unknown whether women or men are more prone to taste PTC. PTC is not actually found in food, but similar chemicals are, so a person's ability to taste PTC will affect food choice to some extent. PTC-like chemicals are found in the Brassica family of vegetables, such as cabbage, brussel sprouts, and broccoli. People who can taste PTC often do not enjoy eating these vegetables, since they taste bitter to them. Non-tasters tend not to notice bitter tastes and therefore may be more likely to become addicted to nicotine (which is bitter).
Most primates still have the ability to taste PTC, suggesting that it plays a role in fitness for survival, specifically because many poisonous plants taste bitter.
