A CODE FOR TRAITS: DNA STRUCTURE AND FUNCTION
NAME______________________________________________DATE_______________PERIOD____
INTRODUCTION
Just as an architect uses a blueprint to construct a building, an organism’s DNA is a blueprint for its traits.
The blueprints for the White House are different from the blueprints for the Washington Monument,
making these two buildings different on a structural level. It makes sense, therefore, that organisms with
different traits must have different DNA; but how is their DNA different? In today’s lab, you will
investigate how differences in DNA can produce differences in human red blood cells.
OBJECTIVE
After completing this investigation, you will be able to explain how a genetic trait is determined by the
code in a DNA molecule.
PROCEDURES
_____ 1. CUT out your 12 nucleotides along the solid lines.
_____ 2. WRITE “Gene From (Mother or Father)” at the top of the plain white paper.
_____ 3. FIND the numbered nucleotides – there should be six. GLUE these nucleotides in numerical
order, beginning with number 1, down the LEFT side of your paper. The tab of one nucleotide
should fit into the notch of the nucleotide before it.
_____ 4. CONSTRUCT the complementary strand of DNA to complete your gene. This step models
the anti-parallel nature of a DNA molecule – one side is “right-side-up” on a molecular level while
the other side is “upside-down”
_____ 5. LABEL your gene as either “normal hemoglobin” or “sickle hemoglobin” according to the key
below. COMPARE your gene sequence to those in the key. RECORD the label to the right of
your gene or at the bottom of your paper.
Label your gene with one of the following:
“N” (normal hemoglobin) if it has the following sequence G G C T T A
“S” (sickle hemoglobin) if it has the following sequence G G C A T A
_____ 6. DRAW the product of your gene on your white paper, according to the information below.
Normal Hemoglobin
Sickle Hemoglobin
_____ 7. SIMULATE sexual reproduction with your partner. COMPLETE the data table below.
MOTHER
FATHER
OFFSPRING
Gene(s)
(use N and/or S)
Type of red blood
cells (draw and
label)
_____ 8. COMPLETE the Analysis Questions.
ANALYSIS QUESTIONS
1. Describe the shape of a real DNA molecule. Be as specific as possible.
2. How many base pairs does your gene have?
3. If a DNA molecule has 8436 Ts, how many As will it have? Justify your answer.
4. Use the template DNA molecule below to construct its complementary strand.
template gene =
A T C G C G A T A A G G C T A G C T G A C
complement = .
5. Will your fictitious child be healthy or have sickle cell anemia? Explain your answer using
information from your data table and incorporating your knowledge of how DNA is a code for traits.
NUCLEOTIDES FOR MOTHER
1
deoxyribose
adenine
thymine
phosphate
group
phosphate
group
adenine
guanine
phosphate
group
deoxyribose
thymine
phosphate
group
phosphate
group
adenine
deoxyribose
guanine
3
guanine
phosphate
group
phosphate
group
deoxyribose
phosphate
group
2
deoxyribose
deoxyribose
4
6
deoxyribose
deoxyribose
deoxyribose
cytosine
phosphate
group
5
deoxyribose
phosphate
group
thymine
deoxyribose
phosphate
group
cytosine
deoxyribose
phosphate
group
cytosine
NUCLEOTIDES FOR FATHER
1
4
deoxyribose
adenine
deoxyribose
thymine
phosphate
group
phosphate
group
deoxyribose
guanine
phosphate
group
6
deoxyribose
adenine
deoxyribose
thymine
phosphate
group
phosphate
group
adenine
deoxyribose
3
guanine
phosphate
group
phosphate
group
guanine
phosphate
group
2
deoxyribose
deoxyribose
deoxyribose
cytosine
phosphate
group
5
deoxyribose
phosphate
group
thymine
deoxyribose
phosphate
group
cytosine
deoxyribose
phosphate
group
cytosine