Lab: Biomolecules, DNA Replication and Protein Synthesis
Introduction:
In this activity, you will work with your team to understand the structure and functions of the nucleic
acids DNA and RNA. DNA is the genetic material that determines how to build a protein, while RNA
aids in protein synthesis.
DNA structure: DNA is a double helix with two sugar-phosphate backbones and paired nitrogen
bases. Adenine (A) is paired with Thymine (T), and guanine (G) is paired with cytosine (C). DNA
makes up the chromosomes that carry the genes.
RNA structure: RNA is composed of one strand of nucleotides. The sugar found in each
nucleotide is ribose and the possible nitrogen bases are adenine (A), uracil (U) instead of thymine,
guanine (G), and cytosine (C).
DNA replication: DNA replication, DNA unzips and a complementary strand forms opposite to
each original strand. This means that replication is semi-conservative because each double helix
contains one old stand and one new strand.
Protein synthesis:
RNA is a single stranded nucleic acid in which A pairs with U (Uracil), while G still pairs with C. The
sugar units used in DNA are deoxyribose; however, the sugar units in RNA nucleotides are
ribose. DNA specifies the synthesis of proteins using a triplet code: every three bases is
transcribed into an mRNA codon that stands for one amino acid. This is the information DNA
passes from generation to generation on the genes.
Protein synthesis involves two major steps, each with its own kind of RNA. In the first step called
transcription,, a messenger RNA (mRNA) molecule will be produced by pairing mRNA nucleotides
with a half “ladder” of a DNA molecule. You will choose one side of your DNA model to use as the
sense side. The sense side is the side with exposed nitrogen bases that will bond to the bases of
the mRNA as it has the code for protein production. This mRNA will leave the nucleus and go to a
ribosome in the cytoplasm. The ribosome is made of ribosomal RNA.
In the second step called translation, the mRNA will attract a second form of RNA called transfer
RNA (tRNA). These tRNAs will bring in amino acids and place them in the proper sequence to
produce the specific protein as ordered by the gene that was transcribed.
Materials required
1. Kit (plastic bag) with the following materials
a) 36 black: deoxyribose sugars
b) 9 purple: ribose sugars
c) 39 white tubes: phosphates
d) 18 white rods: hydrogen bonds
e) 10 orange tubes: adenine
f) 10 green tubes: thymine
g) 5 purple tubes: uracil
h) 8 blue tubes: cytosine
i)
j)
k)
8 yellow tubes: guanine
3 purple rods: tRNA
3 black rods: amino acids with R
groups
l)
2 grey tubes: peptide bonds
m) 1 purple ribosome
2. Copy of the activity
Roles:
Team secretary: you will read the activity to the others, guide the activity along, and write the
answers to the analysis questions. You will help put materials back into the bag.
1
Construction workers: you will build the nucleotides for DNA and RNA and the DNA molecule,
then you will carry out DNA replication and protein synthesis. You will help put materials back into
the bag.
Evidence gatherers: You will take the required pictures, paste them onto the Lab Report, fill in the
report with the answers of all the analysis questions, then turn in the Lab Report via discussion
board.
Instructions
Part A: Building a model of DNA
1. Check to make sure that your kit is complete, by separating the following parts into groups.
2. Build 18 DNA nucleotides by joining a deoxyribose sugar, with a phosphate group and a
nitrogen base (A, T, C, or G). Build 4 each of cytosine and guanine, and 5 each of adenine
and thymine. Take a picture of one of the DNA nucleotides.
3. Use these nucleotides a strand DNA using 9 nucleotides. Take a picture of the DNA
strand that you built. Then, by using complementary base pairing, make a second strand
of DNA. Join it to the first strand with hydrogen bonds. Match nucleotides of adenine
(orange) with thymine (green) and cytosine (blue) with guanine (yellow) using white rods
(hydrogen bonds). You may choose the sequence of bases, buy have at least one of each
color on both sides of your ladder. Bond the phosphate of each nucleotide to the sugar unit
of the neighboring nucleotide. Take a picture of the double stranded DNA molecule
that you built.
Part B: DNA replication
1. Unzip the DNA molecule by separating the 2 original strands at the hydrogen bonds
between the nitrogen bases.
2. Use the original strands of the DNA molecule to make new strands by complementary base
paring.
Part C: RNA and Protein synthesis
Transcription
1. Construct 9 RNA nucleotides that will be complementary to your original strand of DNA.
Take a picture of one of the RNA nucleotides.
2. Construct a mRNA molecule that is complementary to your original DNA strand (gene).
Take a picture of the mRNA strand that you built.
Translation
1. Construct the tRNA molecules by matching three bases that are complementary to the
bases of a codon on the mRNA.
2. Find the amino acids with the specific R-group that matches each tRNA.
3. Attach the tRNAs to their specific amino acids. Take a picture of one of your tRNAamino acid complex.
4. Bring the tRNA-amino acid complex to the codon of mRNA, which codes for that tRNA.
Attach with hydrogen bonds.
5. Attach covalent (peptide) bonds (grey tubes) between adjoining amino acids. These
peptide bonds are formed through a series of dehydration syntheses.
6. Disconnect the polypeptide (amino acid chain) from the mRNA. Take a picture of your
final protein
2
Lab Report for Biomolecules, DNA Replication and Protein Synthesis
Group __405__ Team _2_Names_ Valeria Elizondo Sada A01194577
Instructions:
Paste the pictures solicited as evidence of your understanding of the structures of DNA and RNA
molecules, and the processes of DNA replication and protein synthesis, then answer the
analysis questions. Each picture is worth 10 points, and each analysis question is worth 5.
Pictures
1. A DNA nucleotide
2. A strand of DNA consisting of 9 DNA nucleotides
3. A double stranded DNA molecules with 9 pairs of nucleotides that are complementary
based paired
4. A mRNA with 9 nucleotides derived from your original DNA strand
5. A tRNA with its anticodon and its corresponding amino acid
6. Your final protein
Analysis Questions
1. Compare the structures of DNA and RNA by filling in the chart:
DNA
RNA
Number of strands in the
molecule
Sugar present
Two strands
One strand
Yes; deoxyribose
Yes; ribose
Nitrogen bases
Yes: adenine, guanine,
cytosine, thymine
Yes: adenine, cytosine,
guanine, uracil
2.
What is produced in transcription? mRNA
3.
What is produced in translation? tRNA- amino acid and the final protein in ribosome
4.
If a DNA triplet code is TAC, what is the complementary code of mRNA? The RNA code will
be AUG
5.
If mRNA codons are AUG, GGU, CAG, what three anticodons of tRNA will attach?
The three anticodons of RNA that will attach are UAC, CCA, GUC
6.
What is the source of free amino acids in the cytoplasm?
3
The cytoplasm acquires amino acids from protein found in food turnover and biosynthesis.
7.
If the DNA analysis of a gene shows 20% adenine bases, what would be the percent of
thymine __20%___guanine _30%_and uracil_0%
8.
List by order of size the following: gene, cell, chromosome, atom, nucleus, base subunit,
nucleotides.
Cell, nucleus, chromosome, gene,
nucleotides, base, subunit, atom
4