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Unit 18 – Assignment 1 – P1
DNA
DNA is a nucleic acid
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The two separate chains of nucleotides, held by hydrogen bonds are twisted into a double helix
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The two sides of the double helix are what is known as antiparallel
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They are joined by condensation reactions
...
These bases are linked up by hydrogen bonds
...
It is called ribonucleic acid
...
The nucleotides are bonded by a bond
between the sugar of a nucleotide and the phosphate of another
...
One is called messenger RNA, or otherwise known as mRNA
...
It is there to rewrite the
sequence of bases of a section of DNA
...
mRNA carries the code for forming a specific protein from the nucleus to the
ribosomes in the cytoplasm
...
Messenger RNA allows the genetic coding in DNA
...
It contains
bases Adenine, Guanine, Cytosine and Uracil
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tRNA
The second type of RNA is called transfer RNA, or otherwise known as tRNA
...
tRNA picks up specific amino acids from the
cytoplasm and then brings them into the surface of a ribosome
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This is
called translation
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The

Sugar
DNA has a
sugar called
deoxyribose
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Length

Strands

Location

Function

DNA is
3,000,000
to
4,000,000

DNA is
double
stranded

DNA is
located in
the
nucleus
...


mRNA

tRNA

Four bases
make up
mRNA
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They are: A,
C, G and U
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Four bases
make up
tRNA
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nucleotides
long
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UAG,
CAA,
and
GUC
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an mRNA
in bacterial
systems is
1000 to
1500
nucleotides

mRNA is
located in
the
nucleus
...


AUC,
GUU
and
CAG
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tRNA is
located in
the
cytoplasm
...


the
sequence of
amino acids
in the
protein of
the cells,
such as
enzymes
...

This genetic
code is used
for making a
specific
protein from
the nucleus
to the
ribosomes in
the
cytoplasm
...
It
takes the
specific
amino acids

RNA has the
base uracil
while DNA
has the
base
thymine
...

This is where
they are
joined in a
specific
sequence to
make a
specific
protein
...

Translation - Using the code to make a chain of amino acids

Structure of tRNA:

Transcription
Transcription occurs in the nucleus
...
The mRNA carries genetic information out of nucleus, to ribosomes
in cytoplasm
...
The energy is provided by the reduction of ATP into ADP and Pi
...
The DNA molecule in the region of the gene unwinds
...
The hydrogen bonds between the bases holding the two chains are broken
...
The RNA polymerase, synthesises a complementary mRNA from the template DNA strand
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Translation
Translation occurs in the cytoplasm
...
This
involves 3 different molecules:
•
•
•

tRNA (carrying one amino acid)
mRNA
Ribosome

There are many steps to translation:
1
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2
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It reads bases in groups of three
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Each codon has a complementary
transfer RNA (anticodon), which carries a specific amino acid
...
The anticodon of the tRNA binds to the first codon
...


4
...
This requires
an ATP and an enzyme
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The first tRNA is released by the ribosomes
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The ribosome moves one codon along the mRNA
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7
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8
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9
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Unit 18 – Assignment 1 - M1

DNA

T A C A T

A C T G G T C A C

A A C A T T C G C

T C T T T C A T

G C A T A

A A T A C T A A A

mRNA

A U G U A U G A C C A G U G U U G U U U G C G A G A A A G U A C G U A U U U A U G A U U U

Amino
acid
sequenc
e

M E T T Y R A S P G L N C Y S C Y S L E U A R G G L U S E R T H R T Y R L E U S T O P

To find out the mRNA letters, I used base pairing
...
To find the sequence, I used the first three letters of the mRNA, then found the three letters in
the table
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Each codon has a three digit code which is the short name of the amino acid
...
For example, the code fore UUU is Phe
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However, when I found the code for UGA, it says STOP
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This means that you must stop the sequence and then carry
on with the next sequence
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The codon that marks the start of a protein chain is AUG
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This means that every protein chain must start with methionine
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