Download Grade-Level Science Homework Due: Friday, October 7th, 2011

Grade-Level Science Homework
Due: Friday, October 7
Name: ______________________________
th
, 2011
Teacher: ____________
Period: ____
Part I: Monday’s Investigation Graph
Make sure you complete your histogram or pie chart from Monday’s investigation and turn it in
Part II: Why you look the way you look
Have you ever asked yourself, “Why do I look different than my parents?” The simple answer to that
question is that almost everyone’s DNA (deoxyribonucleic acid) varies (varies = differs). DNA is a large
organic compound located in the nucleus of eukaryotic cells, and it stores all the genetic information needed to
build and operate an organism. In prokaryotic cells, the DNA floats in the cytoplasm. DNA is constructed of 4
smaller, organic compounds called bases. The four different bases are labeled A for adenine, T for thymine, C
for cytosine, and G for guanine. The four bases are used to generate a code, and each person’s DNA or genetic
code is unique (unique = one of a kind). Just like words are created using letters A to Z, life uses 4 different
bases (A, T, C and G) to create a unique, chemical code to construct an organism.
Base pair
1. Which statement is false about DNA?
a. DNA varies or differs between most people
b. DNA is located in the nucleus of eukaryotic organisms
c. DNA is constructed of 4 bases
d. DNA is an inorganic compound
Short piece of DNA
A persons DNA or genetic code mostly controls a person’s traits. Traits are characteristics or features
of an organism; for example, your height is one trait and your eye color is another trait. Each trait is controlled
by a part or section of the organism’s DNA called a gene. A single piece of DNA can include hundreds to
thousands of genes. Earlier, we said that DNA is like a word constructed of four letters, A, T, C and G. It is
better to say that genes are like words, and DNA is a very, very, very long sentence. Just like we shuffle letters
to form words and put words together to form sentences, life shuffles the 4 bases (A, T, C, and G) to form
genes, and puts genes together to form a strand of DNA. When most organisms reproduce, like humans, half of
the child’s or offspring’s DNA comes from mom and the other half comes from dad. This is why we look
similar, but not identical to our parents. The process of passing down DNA and genes from parent to offspring
is known as inheritance.
Now you are asking, “What does DNA look like?” If you imagine a twisted ladder, then you can
imagine the structure of DNA (see picture above). DNA is made up of two strands of bases. The bases on
each strand pair up to form a base pair. Adenine always pairs with Thymine, and Guanine always pairs with
Cytosine. The base pairs make up the steps of the twisted ladder. DNA is an organic compound, but in
addition to carbon and hydrogen, it also includes the elements phosphorous, nitrogen, and oxygen.
2. If genes are like words, then a definition is like a _______.
a. DNA
b. trait
c. base pair
d. inheritance
3. If a person’s traits are mostly controlled by their genes, what other factors or variables could affect a
person’s traits? _______________________________________________________________________
____________________________________________________________________________________
___________________________________________________________________________________.
Part III: Defend Yourselves!
Image a couple of aliens travel to Earth to complete a
descriptive investigation of humans. They observe many
different humans, and conclude that all humans look alike. In
fact, they find humans so boring and ugly that they decide to
destroy us all. You are offended by their conclusion and
angered by their decision. In response, you decide to argue
that they are wrong, and claim that humans are not all alike.
Use the vocabulary words in the box to compose an argument
against the alien’s conclusions.
Vocabulary:
□ DNA
□ Trait (s)
□ Gene(s)
□ Nucleus
□ Cell(s)
□ Variation
□ Parent’s
Dear Kang and Kodos,
I am offended that you think humans are ugly and all look the same. In fact,
__________________ show lots of variation (variation is human word that means
“differences”). For example, some humans have blue eyes while other humans have
green, brown, or grey eyes. And, some humans are tall, while others are short. Each
trait is controlled by at least one __________________ I’m not sure about you, but all of our
genes are coded in our __________________ which stores all of our genetic information. It is
impossible for us to look exactly like our __________________ because our DNA is mixture of
their DNA. Also, our DNA can change because of mutation. When a mutation happens,
a base is changed in our DNA, which can change the function of a gene and create a
whole new trait. Mutations increase the __________________ in a population of organisms.
True, all humans are eukaryotic organisms, and we safely keep our DNA inside the
__________________ of our __________________ but we are definitively not all alike. Finally, you
are the ugly ones; not us! Please don’t destroy us 
Sincerely,
A concerned student of earth