NAME_______________________
DNA, RNA and proteins
Objectives:
1. Be able to identify the building blocks of DNA and RNA.
2. To assemble a strand of DNA and copy it into RNA.
3. To build a polypeptide chain (protein).
Background:
Genes consist of DNA (deoxyribonucleic acid). DNA is made of the sugar,
deoxyribose, phosphate groups and four different bases, adenine (A), cytosine (C),
guanine (G) and thymine (T).
The structure of DNA consists of a chain of alternating sugars (S) and
phosphates (P); the bases form the rungs of the ladder:
P
P
P
P
P
P
P
S
|
C
S
|
G
S
|
A
S
|
T
S
|
A
S
|
C
G
|
S
C
|
S
T
|
S
A
|
S
T
|
S
G
|
S
P
P
P
P
P
Genes carry the information to make the proteins. Proteins determine most
of our traits. The sequence of bases on the DNA (CGATAC..) specifies the code
for the proteins. Proteins are made up of smaller units called amino acids.
To make a protein from a gene involves:
1. TRANSCRIPTION: The DNA containing the gene is copied into
another nucleic acid, messenger RNA. RNA is like DNA except it contains ribose
as the sugar, it has the base uracil in place of thymine and it is always a single
strand.
1
2. Messenger RNA moves to the ribosome, the site of protein synthesis.
3. TRANSLATION:
A. Transfer RNAs, small RNAs that decode the message, bring the amino
acids to the ribosome.
B. The transfer RNAs bind to the messenger RNA. A code of three bases
(codon) is read by each transfer RNA.
C. Protein synthesis occurs when the amino acids carried by the transfer
RNAs are joined together by the ribosome to make a polypeptide chain (protein).
Procedure:
Part 1: Models of DNA, RNA and proteins
Use the DNA puzzle to build a DNA, transcribe it into messenger RNA and
start to build a protein. Note that you may want to use part of each model in the
next one you build.
DNA model
1. Sort out the building blocks for DNA from the other pieces. These are:
--deoxyribose sugars (salmon)
--phosphates (yellow)
--bases (green, blue, blue-green)
2. Build a backbone for the DNA from alternating
sugars and phosphates.
3. Attach the bases to the sugars.
4. Show how the strand of DNA can be copied into
another strand (this process is called REPLICATION).
2
Use the following base pairing rules:
A pairs with T
G pairs with C
messenger RNA model
1. Locate the building blocks unique to RNA. These are:
--ribose sugars (pink)
--uracil (U) base (white)
These are combined with phosphates (yellow) and the other bases to make RNA.
2. Construct a messenger RNA molecule that could be made from one of the DNA
strands you made. The same base pairing rules apply for RNA except uracil (U)
pairs with adenine (A).
Synthesize a protein
1. Identify the special pieces for protein synthesis in the kit. These are:
--the ribosome (large white folded sheet)
--transfer RNAs (large brown or tan cloverleaf)
--amino acids and charging enzymes (brown or tan tiles)
2. Link up the transfer RNAs with the correct amino acids and charging enzymes.
3. Bring together the different components for protein synthesis.
A. Open out the ribosome sheet. Move the messenger RNA to its place on the
ribosome.
B. Find transfer RNAs that can bind two sets of codons on the messenger RNA
(you may need to substitute for some of the bases on your messenger RNA as the
kit can only decode two of the possible twenty amino acids).
3
C. Link together the amino acids on the tRNA in the “A” site to start the protein
chain.
Biology 211 Intro Molecular and Cell Biology Lab
DNA-->RNA--> protein
Assignment: Worksheet
Name___________________
Part I: Review of components involved in decoding genetic information.
1. What is the function of
a. DNA:
b. DNA polymerase:
c. messenger RNA:
d. RNA polymerase
e. transfer RNA:
f. ribosomes:
4
2. What happens in each of the following processes?
a. DNA REPLICATION--
b. TRANSCRIPTION--
c. TRANSLATION--
Part II: Decoding a gene
4. Explain what is meant by the following terms that relate to the genetic code and the
process of translation.
a. codon
b. anticodon
c. start codon
5
d. stop codons
5. Transcribe and translate the code from the DNA molecule given into the correct
messenger RNA (mRNA), and amino acid sequences. (Use the amino acid table below).
DNA
DNA
mRNA
protein
5’
3’
5’
A
T
G
A
U
G
C
A
C
G
G
A
C
6
G
C
T
T
C
G
A
A
T
A
C
T
G
A