Lesson 19, The Race for the Double Helix
Overview of Lesson
- Courses for Which the Lesson is Intended
- Intended for use in a college- preparatory or advanced
high school biology course.
- Types of Teaching/Learning Activities Employed in this
Lesson
- Students work in collaborative groups. Students are
required to use knowledge from the course to solve a
puzzle. The class watches a video. The teacher leads a
student discussion of the ethics/values issues associated
with the student activity and the events depicted in the
video.
- Category that Best Describes this Lesson
- Behavior of scientists.
- Ethics/Values Issues Raised by this Lesson
- Cooperation versus competition in science; attitudes
toward the sharing of unpublished data and results;
assignment of credit for scientific discoveries; sexual
bias in the scientific community.
Back to Top
Lesson Plan
Instructions for the Teacher. This lesson is designed to
explore several common ethics/values issues related to the
behavior of research scientists, while reinforcing students'
understanding of the relationship between the structure of
the DNA molecule and the biology of protein synthesis. It was
inspired by the video The Race for the Double
Helix55, which is a dramatization of the efforts of
James Watson, Francis Crick, Rosalind Franklin, Maurice
Wilkins and other scientists that led to the discovery of the
structure of DNA. The video is, in turn, based on the book
The Double Helix, by James Watson56.
The complete activity requires a minimum of four
forty-minute class periods. It should be used after students
have learned about the structure of DNA, the relationship
between DNA and messenger RNA (mRNA), and the mechanism of
synthesis of proteins using mRNA.
At the beginning of the lesson, the class is divided into
groups of four students each representing a "research team."
The objective of these teams is to win a "bonus" by
deciphering a coded message. This is achieved by first
transcribing a DNA segment, given to the team, into mRNA,
determining the amino acid sequence that is coded on the
mRNA, and then using a code that assigns each amino acid to a
letter or other element of sentence structure.
No single research team is given enough information to
decipher the entire message. Each team is given instructions
on how to interact with the other teams in an effort to win
the bonus. Some of the teams are instructed to behave in a
collaborative manner, sharing their information. A second set
of teams is told to act in a highly competitive manner,
keeping their own results to themselves while aggressively
attempting to obtain data from the others. One team is
instructed to work independently and methodically in an
effort to solve the problem on its own.
The following instructions are based on an assumed class
size of 24. The six four-person research teams will be
labeled Groups A, B, C, D, E and F. Groups A, B, and C will
be instructed to behave as "collaborator" teams. Groups D and
E will be told to behave as aggressive "competitors." Group F
will be the "independent," methodical research team. (In
classes of larger or smaller size, some, or all of the groups
can be increased to five or decreased to three students.
Alternatively, the number of collaborator or competitor
groups can be increased or decreased.)
The first group that brings the correct message to the
teacher wins the bonus. That message is "CONGRATULATIONS! YOU
ARE THE WINNER. THE BONUS IS YOURS!"
The segments of DNA given to each of the groups, when
correctly decoded, will produce the following partial
messages:
Group A: ___________________! YOU ___ ___ WINNER. THE
______ IS YOURS!
Group B: ___________________! YOU ARE THE ________. ___
BONUS __ ______!
Group C: ___________________! YOU ___ ___ WINNER. THE
______ IS ______!
Groups D&E: ___________________! YOU ARE THE WINNER.
___ ______ __ ______!
Group F: CONGRATULATIONS! YOU ARE THE WINNER. THE BONUS IS
SCAT!
Note that by exchanging data, the collaborator groups can
get the entire message, except for the first word, which they
would have to guess. The independent group has a longer
message, which includes the first word, which none of the
other groups have. By working methodically on their own that
group can get an entire message, but the last word is
incorrect and they can get the bonus only by guessing the
correct word. The competitor groups are given the shortest
part of the message, but by following their instructions to
be aggressive, they may be able to find a way to get the rest
of the information. In fact, teachers who have used this
exercise report that it is usually one of the competitor
groups that wins the bonus.
After one of the groups correctly deciphers the message,
the teacher should lead a discussion about the students'
reaction to the activity and their thoughts about how the
instructions given to the groups compare with what they
imagine to be the behavior of real-life scientific
researchers. The teacher should help the students identify
ethics/values issues that are related to the points the
students raise in the discussion.
Discussion Questions
Some questions that the teacher might ask to stimulate and
direct this discussion are
- What do you think about the instructions your research
group was given and did you have any reaction to the
behavior of the other groups?
- Did you have any problem with the way the bonus was
awarded?
- Which of the groups was instructed to behave in a
manner that you think resembles the way real-world
scientists behave?
- What is your opinion about the roles of competition,
collaboration and independent work in scientific
research?
- Are the standards of behavior that you expect of
scientists any different than those you set for other
professional workers?
- When the continuation of this discussion no longer
appears to be fruitful, the students should be shown the
video The Race for the Double Helix. After
viewing the video, the teacher should lead another
discussion.57
Some suggested questions for this second discussion
are
- Which of the scientists depicted in the film behaved in
a manner that resembles the way that your research group
was instructed to behave?
- If you were going to be a scientist, which of the
researchers in the film would you choose to be like?
- Why? (Note: If, as is likely, more girls than boys in
the class identify with the Rosalind Franklin character,
some questions might be asked to get the class to think
about reasons why this is true.)
- What differences did you observe among the research
goals of the various principal researchers - James Watson,
Francis Crick, Rosalind Franklin and Maurice Wilkins?
- Which do you think should be the goal of a scientist:
receiving credit for being the first one to make an
important discovery, or sharing your results with others so
that the discovery can be made as soon as possible, even if
you don't get the credit for it?
- In what circumstances do you think scientists are
justified in not sharing their results with others before
their research is completed.
- This video is based on a book written by James Watson,
in which he very openly described his memory of the effort
leading to the discovery of the structure of DNA. The book
proved to be very controversial, and Watson received much
criticism from other scientists for revealing the personal
side of this historic research effort. Why do you imagine
that other scientists reacted in this way?
- Do you think that women scientists are still
discriminated against the way Rosalind Franklin was in the
1950s?
- Aside from the direct effects of discrimination against
women, can you think of any other possible consequences of
the fact that science has historically been a profession
that has been dominated by men, most of whom had above
average incomes?
Instructions and Handouts for Students
- You will be assigned to a four-student research
group.
- Your group will be given a sequence of nucleotide pairs
carried by a piece of DNA. Using the left hand set of
nucleotides as a template, and your knowledge of the
base-pairing that occurs in RNA, transcribe the
corresponding strand of mRNA.
- As you have learned, each successive set of three mRNA
nucleotides is a codon that codes for a particular amino
acid. Using Table 1, determine the amino acid sequence that
would be produced by the mRNA you transcribed.
- Use table 2 to determine the sequence of characters
(letters, spaces or punctuation marks) that correspond to
your DNA sequence, and write them in the appropriate place
on your data sheet.
Groups A, B and C
- Your group is collaborating with groups B and C (or A
and C, or B and C). After deciphering the part of the
message coded by your piece of DNA, you should share your
results with these other two groups to complete missing
sections of the message indicated by the numbers of spaces
in parenthesis. You should then publish your results on the
black board for the other groups to share. You may then try
to complete any missing part of the message by guessing.
When you think you have the entire correct message, report
it to your teacher who will give a bonus to the first group
that gets it right.
Groups D and E
- Your group is intent on being the first to decode the
entire message. You find that After deciphering the part of
the message coded by your piece of DNA, you are missing
sections of the message indicated by the numbers of spaces
in parenthesis. You should try to obtain the missing
information from the other groups by any means you can
devise, without sharing your results with them. When you
think you have the entire correct message, report it to
your teacher who will give a bonus to the first group that
gets it right.
Group F
- Your group believes in methodical, independent work.
You do not wish to publish your work until you are sure it
is correct. Unfortunately, you find that after you decipher
the message corresponding to your piece of DNA, it contains
an error. You may try to independently deduce (guess) the
correct complete message. Only if you are sure that you
know what it is should you report it to your teacher who
will give a bonus to the first group that gets it
right.
Back to Top
DNA Pieces
| (51 SPACES) |
(24 SPACES) |
|
|
(18 SPACES) |
|
|
| TA |
AT |
TA |
TA |
TA |
CG |
GC |
| AT |
CG |
AT |
TA |
GC |
TA |
TA |
| CG |
AT |
AT |
GC |
GC |
TA |
GC |
| CG |
TA |
TA |
AT |
GC |
GC |
|
| TA |
GC |
TA |
GC |
CG |
TA |
|
| TA |
GC |
TA |
AT |
GC |
TA |
|
| GC |
CG |
AT |
TA |
AT |
TA |
|
| TA |
TA |
TA |
AT |
TA |
TA |
|
| CG |
GC |
TA |
GC |
GC |
CG |
|
| AT |
CG |
AT |
AT |
TA |
GC |
|
| TA |
TA |
TA |
TA |
AT |
CG |
|
| GC |
AT |
GC |
GC |
CG |
AT |
|
Group B
| (51 SPACES) |
|
|
(36 SPACES) |
|
| T A |
CG |
TA |
CG |
GC |
| AT |
CG |
TA |
GC |
CG |
| CG |
TA |
CG |
AT |
AT |
| CG |
TA |
AT |
CG |
AT |
| TA |
TA |
GC |
TA |
TA |
| TA |
CG |
AT |
TA |
GC |
| GC |
TA |
TA |
CG |
(27 SPACES) |
| TA |
AT |
AT |
TA |
|
| CG |
AT |
GC |
GC |
|
| AT |
AT |
AT |
GC |
|
| TA |
TA |
TA |
TA |
|
| GC |
AT |
GC |
TA |
|
Group C
| (51 SPACES) |
(24 SPACES) |
|
|
(18 SPACES) |
| TA |
AT |
TA |
TA |
TA |
| AT |
CG |
AT |
TA |
GC |
| CG |
AT |
AT |
GC |
GC |
| CG |
TA |
TA |
AT |
GC |
| TA |
GC |
TA |
GC |
CG |
| TA |
GC |
TA |
AT |
GC |
| GC |
CG |
AT |
TA |
AT |
| TA |
TA |
TA |
AT |
TA |
| CG |
GC |
TA |
GC |
GC |
| AT |
CG |
AT |
AT |
(18 SPACES) |
| TA |
TA |
TA |
TA |
|
| GC |
AT |
GC |
GC |
|
Groups D and E
| (51 SPACES) |
|
|
|
|
| TA |
CG |
TA |
AT |
TA |
| AT |
CG |
TA |
CG |
AT |
| CG |
TA |
CG |
AT |
AT |
| CG |
TA |
AT |
TA |
TA |
| TA |
TA |
GC |
GC |
TA |
| TA |
CG |
AT |
GC |
TA |
| GC |
TA |
TA |
CG |
AT |
| TA |
AT |
AT |
TA |
TA |
| CG |
AT |
GC |
GC |
TA |
| AT |
AT |
AT |
CG |
AT |
| TA |
TA |
TA |
TA |
TA |
| GC |
AT |
GC |
AT |
GC |
|
|
|
|
|
(57 SPACES) |
Group F
| CG |
GC |
AT |
TA |
AT |
CG |
GC |
| AT |
AT |
TA |
TA |
TA |
TA |
CG |
| AT |
CG |
AT |
CG |
TA |
TA |
AT |
| CG |
CG |
CG |
AT |
TA |
CG |
AT |
| TA |
GC |
CG |
GC |
AT |
TA |
CG |
| TA |
TA |
TA |
AT |
TA |
GC |
CG |
| CG |
TA |
TA |
TA |
TA |
GC |
AT |
| TA |
GC |
GC |
AT |
AT |
TA |
CG |
| AT |
TA |
TA |
GC |
TA |
TA |
TA |
| GC |
GC |
CG |
AT |
GC |
CG |
AT |
| AT |
AT |
AT |
TA |
TA |
CG |
GC |
| AT |
CG |
TA |
GC |
TA |
AT |
TA |
| TA |
TA |
GC |
AT |
GC |
AT |
AT |
| TA |
CG |
CG |
CG |
AT |
TA |
|
| TA |
CG |
CG |
AT |
GC |
GC |
|
| CG |
TA |
TA |
TA |
AT |
TA |
|
| CG |
GC |
TA |
GC |
TA |
GC |
|
| AT |
GC |
TA |
GC |
AT |
GC |
|
| TA |
CG |
CG |
CG |
GC |
GC |
|
| TA |
GC |
TA |
TA |
AT |
CG |
|
| AT |
GC |
AT |
GC |
TA |
GC |
|
| GC |
TA |
AT |
CG |
GC |
AT |
|
| TA |
AT |
AT |
TA |
CG |
TA |
|
| CG |
AT |
TA |
AT |
GC |
GC |
|
| GC |
TA |
AT |
TA |
AT |
CG |
|
The Amino Acids
| Abbreviation |
Name |
Abbreviation |
Name |
| gly |
glycine |
ala |
alanine |
| val |
valine |
ile |
isoleucine |
| leu |
leucine |
ser |
serine |
| thr |
threonine |
pro |
proline |
| asp |
aspartate |
glu |
glutamate |
| lys |
lysine |
arg |
arginine |
| asn |
asparagine |
gln |
glutamine |
| cys |
cysteine |
met |
methionine |
| trp |
tryptophan |
phe |
phenylalanine |
| tyr |
tyrosine |
his |
histidine |
| term |
termination |
|
|
Table 1: The Genetic Code: Codons and the Amino
Acids They Code
| First Two Nucleotides
of the Codon |
Last Nucleotide of
the Codon |
| U |
C |
A |
G |
| UU |
phe |
phe |
leu |
leu |
| UC |
ser |
ser |
ser |
ser |
| UA |
tyr |
tyr |
term |
term |
| UG |
cys |
cys |
term |
ttrp |
| CU |
leu |
leu |
leu |
leu |
| CC |
pro |
pro |
pro |
pro |
| CA |
his |
his |
gln |
gln |
| CG |
arg |
arg |
arg |
arg |
| AU |
ile |
ile |
ile |
ile |
| AC |
thr |
thr |
thr |
thr |
| AA |
asn |
asn |
asn |
asn |
| AG |
ser |
ser |
arg |
arg |
| GU |
val |
val |
val |
val |
| GC |
ala |
ala |
ala |
ala |
| GA |
asp |
asp |
glu |
glu |
| GG |
gly |
gly |
gly |
gly |
Table 2 Amino Acid to Character
Conversion
| Amino Acid |
Character |
Amino Acid |
Character |
Amino Acid |
Character |
| Glycine |
A |
Alanine |
B |
Valine |
C |
| Isoleucine |
E |
Leucine |
G |
Serine |
H |
| Threonine |
I |
Proline |
L |
Aspartate |
N |
| Glutamate |
O |
Lysine |
R |
Arginine |
S |
| Asparagine |
T |
Glutamine |
U |
Cysteine |
W |
| Methionine |
Y |
Tryptophan |
D |
Phenylalanine |
J |
| Tyrosine |
Space |
Histidine |
! |
Termination |
. |
RACE FOR THE DOUBLE HELIX -- DATA
SHEET
Name ______________________ Group _____ Period _____ Teacher
____________________
| DNA |
mRNA |
Amino Acid |
Character |
|
DNA |
mRNA |
Amino Acid |
Character |
|
DNA |
mRNA |
Amino Acid |
Character |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
| ____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
|
____ |
____ |
_______ |
______ |
| ____ |
____ |
|
|
|
____ |
____ |
|
|
|
____ |
____ |
|
|
Back to Top
Discussion
substantial investment of classroom time, teachers who
have used it with properly prepared students commented that
it serves to concretize the mechanism by which DNA codes for
protein synthesis, while stimulating very rich and rewarding
student discussions of important ethical issues related to
the behavior of scientists.
In the discussions, it is important to direct attention to
the significance and generality of the issues, rather than
the particular circumstances of the student exercise, or the
specific personality traits of the characters in the video.
These general issues include the common conflict between a
scientist's personal values, such as the desire to achieve
success or fame, and the ethical demands of the scientific
profession. Students should be challenged to consider why
collaboration, sharing of information and the fair assignment
of credit for discoveries are important to the advancement of
scientific knowledge, but may often be compromised due to the
fact that scientists are human beings with competing personal
needs and desires. An effort should be made to take the
discussion arising from the constraints imposed on women in
science beyond the obvious negative aspects of overt sexism
or racism. A possible way to do this is to ask students to
consider whether the ranking of the importance of research
problems by women or minority members might be significantly
different from the choices made by relatively affluent white
males.
For those teachers who can not devote four classroom
periods to this lesson, the required time can be cut in half
by eliminating either the viewing of the video and related
discussion, or the DNA coding exercise. While this
significantly reduces the student experience that can be used
to probe the issues, teachers report that worthwhile
ethic/values education is still achieved.
Steven Angell and Marcia
Brandeau
Longwood High School, Middle
Island
James Baglivi and Mary
Loesing
Shoreham-Wading River High
School, Shoreham
Theresa Dana, Deer Park High
School, Deer Park
Jack Waszmer, Paul Gelinas, Junior
High School, Setauket.