DNA replication, transcription, and translation

GUIDE QUESTIONS
Q1. What are the components of the DNA and RNA
molecule?
Fill in the comparison table below.
Basis of Comparison DNA RNA
1. Number of Strands 2 1
2. Location in the cell nucleus cytoplasm
3. Type of sugar deoxyribose ribose
4. Nitrogenous base pair A,T,C,G A,U,C,G
ANSWER: Sugar
Phosphate Group
Nitrogenous Base

GUIDE QUESTIONS
Q2. What is the structural difference between DNA and
RNA?
DNA and RNA are different in the following:
a. DNA is double stranded while RNA is single-
stranded.
b. The sugar in DNA is deoxyribose while that in RNA is
ribose.
c. The nitrogen bases in DNA are adenine (A), guanine
(G), thymine (T) and cytosine (C). In RNA are adenine,
guanine, cytosine and uracil.

GUIDE QUESTIONS
Q3. What nitrogenous base is found in RNA but not in
DNA?
Uracil

(DEOXYRIBONUCLEIC ACID)
- is the main component of chromosomes
(packaged form of the DNA)

(DEOXYRIBONUCLEIC ACID)
- is the material that transfers genetic
characteristics in all life forms
Where is
DNA
found?

- has three main components:
1. deoxyribose (a pentose sugar)
2. base (there are four different ones)
3. phosphate

- formed by the condensation of a pentose sugar,
phosphate and one of the 4 bases

Nucleotides are linked together by covalent bonds called
phosphodiester linkage

-are divided into two groups:
Pyrimidines (are single ring bases.)
Nitrogenous Bases:
C
C
C
C
N
N
O
N

Pyrimidines (made of one 6 member ring)
Thymine
Cytosine
Nitrogenous Bases:
C
C
C
C
N
N
O
N
cytosine
C
C
C
C
N
N
O
O
thymine
C

Purines (made of a 6 member ring, fused
to a 5 member ring; double ring bases)
Nitrogenous Bases:
C
C
C
C
N
N
N
N
N
C

Purines (made of a 6 member ring, fused
to a 5 member ring; double ring bases)
Adenine
Guanine
Nitrogenous Bases:
C
C
C
C
N
N
N
Adenine N
N
C
C
C
C
C
N
N
O
N
Guanine N
N
C

• Adenine and Thymine always join
together because they form two H
bonds with each other
A T
• Cytosine and Guanine always join
together because they form three H
bonds with each other
C G

The strands
run opposite
of each other.
The 5’ end
always has the
phosphate
attached.
5’ 3’
3’ 5’

-is a very long polymer that is double helix with about 10
nucleotide pairs per helical turn

James D. Watson and Francis Crick,
co-originators of the double-helix
model.

• The backbone of
the molecule is
alternating
phosphates and
deoxyribose
sugar
• The teeth are
nitrogenous
bases.
phosphate
deoxyribose
bases

• One strand of
DNA is a polymer
of nucleotides.
• One strand of
DNA has many
millions of
nucleotides.
nucleotide

22
• Remember, DNA
has two strands
that fit
together
something like a
zipper.
• The teeth are
the nitrogenous
bases but why
do they stick
together?

C
C
C
C
N
N
O
N
C
C
C
C
N
N
O
N
N
N
C
• The bases attract each
other because of
hydrogen bonds.
• Hydrogen bonds are weak
but there are millions
and millions of them in a
single molecule of DNA.
• The bonds between
cytosine and guanine are
shown here with dotted
lines

DNA by the Numbers
• Each cell has about 2
m of DNA.
• The average human has
75 trillion cells.
• The average human has
enough DNA to go from
the earth to the sun
more than 400 times.
• DNA has a diameter of
only 0.000000002 m.
The earth is 150 billion m
or 93 million miles from
the sun.

What does
DNA do?
DNA stores an organism's genetic
information and controls the production of
proteins and is thus responsible for the
biochemistry of an organism.

Where does
REPLICATION
happen?
Inside the
Nucleus

When does
REPLICATION
occur?
occurs during
S phase of the
cell cycle.

--- is the process of producing two identical
replicas from one original DNA molecule that
occurs in all living organisms.
--- is the basis for biological inheritance.

--- is a semi conservative
means that each
daughter DNA consists
of half parental DNA and
half of new DNA

2 old
strands
2 new
strands
SEMICONSERVATIVE
and
SEMIDISCONTINOUS
5’

•DNA double helix unwinds
 Helicase is the enzyme that splits the two
strands. The structure that is created is known
as "Replication Fork".

•DNA now single-stranded
 Single-Strand DNA Binding Proteins (SSB) for
work to bind individuals strands in a DNA
double stranded helix and aid the helicases in
opening it up into single strands. They are
particularly useful in stabilizing the unwound
single-stranded formation.

•New DNA strand forms using complementary base
pairing (A-T, C-G)

Example of DNA Replication
5’ TAC CGG AAT GCA ATG CAT ATG 3’ OLD
3’ ATG GCC TTA CGT TAC GTA TAC 5’ OLD
5’ TAC CGG AAT GCA ATG CAT ATG 3’ OLD
3’ ATG GCC TTA CGT TAC GTA TAC 5’ NEW
5’ TAC CGG AAT GCA ATG CAT ATG 3’ NEW
3’ ATG GCC TTA CGT TAC GTA TAC 5’ OLD

•Used to prepare DNA for cell division
•Whole genome copied/replicated

The following is the base sequence on one
strand of a DNA molecule. If replicated, write the
complimentary strands.
1. A A T G C C A G T G G T
2. C C T G A C T A A T C G
3. G G A C T G A T T C G G
4. T G G C C T A T A T C C
5. G T C A C T G C C G G A

(RIBONUCLEIC ACID)
- Usually one strand

(RIBONUCLEIC ACID)
- The sugar is ribose

(RIBONUCLEIC ACID)
- Contains uracil (U) instead of thymine (T)

(RIBONUCLEIC ACID)
- can both store information and catalyze
chemical reactions.
- is used in protein synthesis

(RIBONUCLEIC ACID)
1. messenger RNA (mRNA)
-brings information from the
DNA in the nucleus to the
cytoplasm(cytosol).
2. ribosomal RNA (rRNA)
-holds tightly to the mRNA and
use its information to
assemble amino acids.

(RIBONUCLEIC ACID)
3. transfer RNA (tRNA)
-attaches the correct amino
acid to the protein chain that is
being synthesized in the
ribosome

-is the process by which genetic information from
DNA is transferred into RNA. DNA sequence is
enzymatically copied by messenger RNA (mRNA)
to produce a complementary nucleotide transfer
RNA (tRNA) strand.
-synthesis of mRNA from a DNA template

-only one strand of DNA, the antisense strand or
template strand, is used to make mRNA
– is the non transcribed
strand
-mRNA is complementary to the antisense strand

Protein Synthesis Transcription
Transcription process
•RNA polymerase attaches to DNA at
a special sequence that serves as a
“start signal”.
•The DNA strands are separated and one
strand serves as a template.
•The RNA bases attach to the
complementary DNA template, thus
synthesizing mRNA.

Protein Synthesis: Transcription
•The RNA polymerase recognizes a
termination site on the DNA molecule and
releases the new mRNA molecule.
(mRNA leaves the nucleus and travels to
the ribosome in the cytoplasm.)

Protein Synthesis: Transcription

DNA
Cytoplasm
Nucleus
Eukaryotic Transcription
Export
G AAAAAA
RNA
Transcription
G AAAAAA
RNA
Processing
mRNA

Where does
TRANSCRIPTION
happen?
Inside the
Nucleus
http://novella.mhhe.com/sites/0070070017/
student_view0/biology_1/chapter_17/mrna
_synthesis__transcription___quiz_2_.html

-process of converting information in mRNA into a
sequence of amino acids (polypeptide chain) in a
protein
-mRNA is in ribosome
-Each combination of 3 nucleotides on mRNA is
called a codon or three-letter code word.
-Each codon specifies a particular amino acid that
is to be placed in the polypeptide chain (protein).

H
P
O
O
HO
O
O
CH2
NH2N
NH
N
N
HOH
P
O
O
HO
O
O
CH2
NH2
N
N
N
N
H
P
O
OH
HO
O
O
CH2
NH2
N
N
N
N
O
A Codon
Guanine
Adenine
Adenine
Arginine

-tRNA brings amino acids to mRNA in the
ribosome

 AUG (methionine) serves as the “initiator”
codon, which starts the synthesis of a protein
 UAA, UAG, and UGA are stop codons, which
signify the end of a polypeptide chain (protein).

Ribosomes
• 2 subunits, separate in cytoplasm until
they join to begin translation
• Large
• Small
• Contain 3 binding sites
• E
• P
• A

E
P A
Large subunit
Peptidyl-tRNA binding site
Aminoacyl-tRNA binding site
mRNA
5’
Exit
site
Small subunit
3’

A
E
Ribosome P
Phe
Leu
Met
Ser
Gly
Polypeptide
Arg
Aminoacyl tRNA
UCUCCA
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA5’
mRNA
3’

A
E
Ribosome P
CCA
Arg
UCU
Phe
Leu
Met
Ser
Gly
Polypeptide
mRNA
3’

A
E
Ribosome P
Aminoacyl tRNA
Ala
CCA
Arg
UCU
Phe
Leu
Met
Ser
Gly
Polypeptide
mRNA
3’

A
E
Ribosome P
Arg
UCU
Phe
Leu
Met
Ser
Gly
Polypeptide
CGA
Ala
mRNA
3’

Determine the protein formed by the following old DNA strand:
CCCATGGAGCGAGAGTTACCGGGTTAGAGGCAC
new strand:
mRNA:
tRNA:
Protein (Amino Acids):

Determine the protein formed by the following old DNA strand:
AGCATGTGCTACTAGCCGGTGAGC
new strand:
mRNA:
tRNA:
PROTEIN (Amino Acids):

Determine the protein formed by the following NEW DNA strand:
TGCCGCCAGTCGCTCGGG
a. normal
b. If in the process of transcription, all of the purine,
GUANINE is changed to cytosine
c. If during transcription, all thymine bases are deleted or
not read by the mRNA.
d. If all cytosine will be substituted by adenine.

DNA replication, transcription, and translation

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