Download Name - O. Henry Science

Pre- AP Science Homework
Due: Friday October 17, 2014
Name: ______________________________
Teacher: ____________
Period: ____
Part I: Why you look the way you look
Directions: Underline key terms, phrases, and ideas in the reading below. Then, answer the questions
that follow.
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 person’s 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 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 _____________ is like a definition.
a. DNA
b. trait
c. base pair
d. inheritance
3. Critical Thinking: If a person’s traits are mostly controlled by their genes, what other factors or
variables could affect a person’s traits?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Part II: Defend Yourselves!
Imagine 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 you claim that humans are not all
alike. Use the vocabulary words in the box to compose an
argument against the aliens’ conclusions.
Vocabulary:
□ DNA
□ Trait (s)
□ Gene(s)
□ Nucleus
□ Cell(s)
□ Variation
□ Parent’s
Dear Kang and Kodos,
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
Sincerely,
A concerned student of earth