Name___________________
DNA Answer Key for 2016
1. What is the full name of DNA? _deoxyribonucleic acid
What is the name of its shape? __double helix
What are the two main roles of DNA? (a) to copy, both for mitosis and heredity
(b) to cause amino acids to do things in the organism
2. Draw a DNA model below, to show all six substances named in full, and with 4 different arrangements
for the “rungs” of the ladder. Have a key for each of the substances.
Draw a model, and label or color key the following: sugar and phosphate (the uprights), and adenine
matched with thymine, cytosine matched with guanine. Make sure you show T ~ A, then A~T, and C~G,
then G~C. you may want to code the sugar as S and the phosphate as P. Here goes my keyboarded
attempt, but somehow do better to show how it’s twisted with your drawing
P
S
P
A ~
T
P
S
P
C ~
G
P
S
S
P
G ~
C
P
S
S
S
P
T ~
A
S
3. Complete the 4 frame drawing of DNA with TTA GAC codons showing how it replicates.
At rest Frame 1
Unzipping Frame 2
Gathering matching bases - Two new DNA result 4
3
T~A
T
A
T
T~A
T~A
T~A
T~A
T
A
T~A
T~A
T~A
T~A
A~T
A
T
A
A~ T A ~ T
A~T
G~C
G
C
G~C
C G~C
G~C
A~T
A
T
A
T A~T
A~T
C~G
C
G
C~G
G C~G
C~G
4. Draw two codons of DNA below such that unzipped RNA from it will result in the Amino Acid
Methione, then show the snippet of DNA (now RNA unzipped), then showing it going to the ribosome.
(See the code at the end of this document to figure out that ATG is what makes the ribosome produce
Methione. )
At rest
Partially unzipped
T~A
A~T
C~G
T ~A
G~C
C~G
T
A
C
T~A
G~C
C~G
A
T
G
What the Ribosome sees
A
T
G
What the ribosome makes
Methione
5. Complete the table below by listing the three basic kinds of DNA mutations, and by providing an
example.
Kind of mutation
Example: 2 codons before
After mutation
mutation
AATCGG
AAATCGG
Insertion
Deletion
AATCGG
ATCGG
Substitution
AATCGG
AATCCG
6. On a separate sheet of paper, write at least 250 words (about a page) describing the history behind the
discovery of DNA. Include the person who originally isolated DNA, and the persons who were credited
with discovering the structure of DNA.
The story begins in Switzerland in the mid 1800’s, where Frederich Miescher was a young doctor who
could not practice since he was hard of hearing. So he did some research, trying to find out what
made up white blood cells and red blood cells. To do his work, he went to hospitals in the city, and
collected their bandages from operations. He analyzed all the blood and tissues, and discovered
something he called nucleic acid. We now call it DNA. He didn’t know its structure or how it worked,
but he figured that it must be pretty important. Fast forward about a century, and Erwin Chargoff
was a Jewish person in Germany worried about the Nazi’s. So, he left. Smart move. On to the U.S.,
where he followed up on Miescher’s work, and analyzed all the plants and animals he could, to see if
he could learn more than Miescher had. What he found was that the Nucleic Acid had some Oxygen
holding it together, as well as Phosphate, changing its name to Oxyribonucleic Acid. He also
discovered that it had these four compounds Adenine, Thymine, Cytosine, and Guanine. The weird
thing was that for different organisms, the amount of Adenine would be way different from the
amount of Cytosine. However, for ALL of them, the Adenine was always equal to Thymine, and the
Cytosine was equal to Guanine. So, he made that a rule, called Chargoff’s Rule. He wasn’t sure what
it meant exactly, but he figured it must be important. Now, we go forward about 15 more years,
and there’s a race to find out the structure of this thing, and how it operates. Rosalind Franklin
made a great advance by taking an XRay picture of it (photo 51), that demonstrated it was a double
helix (hence, the “de” part of the name). Someone else took her photo and gave it to James Watson
and Francis Crick, along Maurice Wilkins, which caused an “aha” moment, so they could then
complete the structure as we now know it. As they wrote, the structure suggests how it must copy
itself. They got the Nobel Prize, and lots of money. Good for them. Rosalind got cancer and died
before all the awards were handed out, so some say she got a raw deal. Oh, not to forgot, Pauling in
the U.S., he was pushing for the single helix model. Wrong, but there is not a doubt but that his
pushing and getting close to the end target caused Watson and Crick to complete their model first.
Protein
(amino
acid)
Alanine
/A
Arginine
/R
Asparagine
/N
Aspartate
/D
Cysteine
/C
Glutamate
/Q
Glutamine
/E
Glycine
/G
Histidine
/H
Isoleucine
/I
START
Codons/
A Purpose*
GCT, GCC, GCA, GCG
CGT, CGC, CGA, CGG, AGA, AGG
AAT, AAC
GAT, GAC
TGT, TGC
/
CAA, CAG
/
GAA, GAG
/
GGT, GGC, GGA, GGG
/
CAT, CAC
/
ATT, ATC, ATA
Amino acid
Codons
Leucine
/L
Lysine
/K
Methione
/M
TTA, TTG, CTT, CTC, CTA,
CTG
AAA, AAG
Phenylaline
/F
Proline
/P
Serine
/S
Threonine
/T
Tryptophan
/W
Tyrosine
/Y
Valine
/V
STOP TAA, TGA, TAG
ATG
TTT, TTC
CCT, CCC, CCA, CCG
TCT, TCC, TCA, TCG,
AGT, AGC
ACT, ACC, ACA, ACG
TGG
TAT, TAC
GTT, GTC, GTA, GTG
TAR, TRA