Download Traits Booklet traits_intro_ws

Name_____________________ period _____
Traits - an introduction to
inheritance/heredity.
Traits are the characteristics of an organism that vary from individual to
individual. This includes external characteristics (such as face shape, hair & eye
color, etc.) and also internal characteristics (blood type, organ structure and
functioning, etc.) While you share many of your characteristics with your parents,
your classmates, a chimpanzee, a bumblebee, a carrot, and even bacteria… no two
organisms are exactly alike (even identical twins).
Why are we so different? We look out at our classmates and identify each
other through very different traits. Even identical twins are not the same though
they have the same DNA. At the same time, there are things that stay the same. . .
we have 2 arms, 2 legs, 10 toes (hopefully). Why are we so similar?
The other day we did histograms (graphs that show how often a certain trait
occurs in our classroom population). Try to answer the following analysis questions
using these histograms. You may discuss these questions with your group, but DO
NOT COPY.
1.
(a) For which trait is there the least variability? ________________
(b) Why do you think this so?
Intro to Dominant and Recessive Alleles: PTC Tasting & Hairline Type
The ability to taste PTC is controlled by a single gene. As with all traits, you
inherit 1 copy of the gene from your
and 1 from your
.
Therefore you have 2 versions of a gene for each trait. Each version of a gene is
called an allele .
PTC Tasting: The ability to taste PTC is dominant over the non-tasting trait. This
means that you only need ONE allele for tasting to express the trait (be able to
taste PTC). Non-tasting is then said to be recessive- meaning that you would need
to have both ‘non-taster’ alleles to express this trait (not be able to taste PTC).
See the chart below:
T= Taster allele
t= Non-taster allele
GENOTYPE: genetic makeup of an
organism – i.e. the two alleles for the
specific trait. There are 3 possible
genotypes for PTC tasting
TT= 2 dominant alleles
PHENOTYPE: the characteristic or
trait – in this case a taster or a nontaster of PTC
Tt (or tT)= 1 dominant, 1 recessive allele
tt= 2 recessive alleles
2. Based on the chart, would you expect that most people are tasters or nontasters? Why?
3. Does the classroom data support this? Justify your answer.
4. My phenotype is:
taster
non-taster
(circle one)
5. Can you determine your genotype? If yes, what is it? If no, why not?
Hairline Type: the presence of a widow’s peak is also a dominant trait.
6. Complete the following chart (use a H for the dominant allele, h for the
recessive allele):
Possible Genotypes
Expressed Phenotype
7. My phenotype is: ___________________
8. Can you determine your genotype? If yes, what is it? If no, why not?
9. Based on the chart, what trait would you expect most people to have? Why?
10. What percentage of our class has a widow’s peak? ______
11. Propose a possible explanation for the mismatch between what you would
expect (#9) and the actual data (#10).
Gender Influenced (sex-linked) traits
12. Which of the traits appear to be related to the gender of an individual?
Nature vs. Nurture
13. Some human traits can be changed by human intervention (or environmental
factors) and others cannot (they are purely genetic).
a. Give examples of traits that cannot be affected by human intervention
(are purely genetic)
i. From the activity
ii. Other example(s)
b. Most traits actually reflect an interaction between genetic and
environmental factors. Give examples of some traits that fall into this
category and explain how they are affected by both genetics and
environmental/human intervention.
i. From the activity
ii. Other example(s)
14. Describe some of the benefits of human genetic variation (ie. Why is it good
that we don’t all look/function exactly the same?)
15. Describe some problems that can result from genetic variation.
Now then, consider the big question. Why are we so different? What makes
us the same? Try to think of some answers from a scientific perspective with
your new information. You will be asked these questions throughout the unit.