A-J Review Sheet (Central Dogma of Biology)
Part A: What does the acronym DNA stand for? ___Deoxyribonucleic Acid_____________________
It was discovered that the smallest section of a DNA molecule that can still be considered DNA is
called a nucleotide. One DNA nucleotide consists of 1 Five Carbon _sugar + 1 phosphate group + 1
nitrogen base. Two scientists,
Watson
and
that DNA consists of a double_ helix
alternating
Crick
determined
, in which the sides are composed of
sugar (deoxiribose)
& phosphate groups , and in which the steps (rungs)
are composed of 2 nitrogen bases
held together by a weak Hydrogen
_ bonds. The
sequence of the bases (or rungs of the ladder) is unique for each person and provides a blueprint /
recipe
for how to make the human body.
1. To serve as the genetic code for any organism, a DNA molecule must be capable of storing large amounts of
varying information. How does the structure of a DNA molecule help it store large amounts of
information? Spirals (double helix) and then coils around Histone proteins
2. Why is DNA often called the blueprint for life?
Because it contains the instructions for how to build
a body like blueprints have the instructions for how to make house
Part B: DNA is the blue print of life.
DNA is found within the nucleus
billion
of every cell in the human body. It is approximately 3
nucleotides long and contains thousands or millions of genes. These genes, can be read like the
chapters in book – each telling their own unique story. In the 1990’s scientists embarked on an important
project to sequence the entire human genome
are 99.9 % identical to each other and
. During this project they discovered that humans
50 % identical to bananas! Since the conclusion of this project
scientists have begun to use the sequence to find the causes of diseases in humans. Some of the diseases they
have linked to our DNA are: tay sachs, cancer, Alzheimer’s, . .
, and
. While we are still unable to cure all the worlds diseases, we hope that learning more about our
DNA we will help us someday achieve this goal.
Part C: To serve as the genetic code for any organism, a DNA molecule must also be capable of copying itself.
When does a cell replicate its DNA?
Cell replicates its DNA during the S phase of interphase to
guarantee that each new cell created during division will have an exact copy.
The process of DNA replication begins when the weak Hydrogen _ bonds break with the
help of the helicase
enzyme. This allows the DNA molecule to unzip
down the middle of its length resulting in 2 open strands. Immediately the enzyme DNA polymerase
attaches new nucleotides
and C
to each open strand of DNA, with A
_always attaching to T
always attaching to G. Finally the 2 newly formed DNA strands zip back up and recoil to
form 2 identical DNA double- helixes
. Each DNA helix is 50
new DNA. This follows the semi-conservative
replication a mutation
% parental DNA and 50%
model. When an error occurs during
can occur. However, the specific enzymes within the nucleus check for
these ‘mistakes.’
Part D: What does the acronym RNA stand for? _Ribonucleic Acid
RNA differs from DNA since it uses Ribose
to make a
single
nucleus
___
sugar and the nitrogen base
stranded molecule. All RNA is made in the
of eukaryotic cells through the process of
. All living things on Earth contain three types of RNA.
ribosomes, while
tRNA
mRNA
Uracil
transcription
rRNA is used to build
relays information from the DNA to the ribosome, and .
transfers amino acids to where they are needed.
Part E: An essential step in the process of protein synthesis is transcription of the DNA code to mRNA.
Transcription occurs in the
nucleus
of the cell where the DNA is located.
The process of transcription begins when a section of DNA called a promoter
allows a single strand of
mRNA
is controlled by an enzyme called
complementary
unzips and
_to form along it. The process of unzipping the DNA
RNA Polyermase
. The RNA strand that is produced is a .
copy of the original DNA. For example if the DNA template strand reads
ATC GAT then the RNA will read
UAGCUA
until the ribosome reaches a stretch of DNA called a
. This process continues
terminator
.
A codon is a specific group of
There are
64
while three code for
3
nitrogen bases on a
mRNA
molecule.
different codons. Sixty-one of these codons attract a specific amino acid,
stop
.
AUG
is the start codon.
Part F: An essential step in the process of protein synthesis is translation of the mRNA codon into a
functioning protein.
Translation occurs in the
20
cytoplasm
of the cell and requires the presence of life’s .
common amino acids. These amino acids are present in our cells thanks to the food
we eat. Translation begins when a ribosome begins to move along a mRNA strand
read its codons. At the
start
___ to
codon the first tRNA anticodon will attach. From here, as each
codon is read it will attract a specific
anticodon or tRNA molecule
,which will bring a
specific amino acid with it. These amino acids will connect to each other, one at a time, by a peptide
bond. The process continues until the ribosome reaches a
stop
codon. At this
point the mRNA, tRNA and rRNA will be released from one another so they can be
recycled
within the cell. The chain of amino acids is called a ___polypeptide
. This molecule will then combine with other polypeptides, fold forming Hydrogen bonds
and create a functional
protein
.
Part G: Critical Thinking Questions:
1. Why don’t all human beings look and act identical? (use the words DNA and protein in your answer)
Our genome is slightly different. Therefore our DNA is transcribed into slightly different codons of mRNA
which are translated into different sequences of amino acids. We do not have the same proteins.
2. Think about what DNA and protein is composed of (hint their monomers). Where does your body get
the nucleotides and amino acids needed to make more DNA and protein?
We get the nucleotides to build new DNA and RNA, and the amino acids to build new proteins from the food
that we eat.
3. Let’s say I wanted to build a protein that was 500 amino acids long…
a. How long would the DNA that codes for that protein be (in terms of bases)?
1500
b. How long would the mRNA that codes for that protein be (in terms of bases)?
1500
c. How many codons of mRNA would code for that protein?
500
d. How many tRNA molecules would need to be used to make that protein?
500
Part H: Comparing DNA to RNA – place at least 6 pieces of information in the Venn Diagram
Double Helix
Deoxiribose Sugar
Thymine
A, C, G
phosphate sugar
backbone
Single Stranded
Ribose Sugar
Uracil
Part I: Comparing replication, transcription and translation.
Process
Where it Occurs
Replication
Nucleus
Transcription
Translation
Nucleus
Cytoplasm
What molecules are
involved
DNA, DNA helicase,
DNA polyermase
DNA, all types of
RNA, RNA
polymerase
mRNA, tRNA,
rRNA, amino acids,
various enzymes and
ATP (energy)
Where it starts
and stops
All over (bubbles
form and eventually
connect)
Promoter to
terminator
Start codon to
Stop codon
What it creates
DNA
All types of RNA
Protein
Part J: Comparing mRNA, tRNA, and rRNA
Type of RNA
Structure
Function
mRNA
Single short strand (3 letters = codon)
Carry the message of how to make the
protein
tRNA
Folded t like structure carrying an
amino acid (3 letters = anticodon)
Transfer the ingredients for the protein
(amino acids)
rRNA
Folded into a ribosome
Make the protein
Part K: Coding
DNA template
DNA complementary
strand
mRNA codon
tRNA anticodon
amino acids
(remember to use
codons)
ATA CGC GGG
TAT GCG CCC
UAU GCG CCC
AUA CGC GGG
Tyr – Ala- Pro