Biochemistry
FIRST YEAR - FINAL TERM MRS. CECILIA VILLANUEVA 11/2021 - 01/2022
Protein Synthesis
DNA Replication
• DNA must be copied
• The DNA molecule produces 2 IDENTICAL
new complementary strands following the
rules of base pairing: A-T, G-C
• Each strand of the original DNA serves as
a template for the new strand.
• Semiconservative Model:
• Watson and Crick showed: the two strands of
the parental molecule separate, and each
functions as a template for synthesis of a new
complementary strand.
1. Why is replication necessary?
So, both new cells will have the correct DNA
2. When does replication occur?
During interphase (S phase).
3. Describe how replication works.
Enzymes unzip DNA and complementary
nucleotides join each original strand. Transcription & Translation
4. Use the complementary rule to create
the complementary strand:
A---T
G---C
C---G
T---A
A---T
G---C
A---T
G---C
C---G
A---T
, Biochemistry
FIRST YEAR - FINAL TERM MRS. CECILIA VILLANUEVA 11/2021 - 01/2022
Protein Synthesis
• DNA can “unzip” itself and RNA nucleotides • When RNA molecules are formed, both the
match up to the DNA strand. introns and the exons are copied from
• RNA molecules are produced by copying the DNA.
part of the nucleotide sequence of DNA into • introns are cut out of RNA molecules while
a complementary sequence in RNA they are still in the nucleus.
• required enzyme = RNA polymerase • exons are then spliced back together to
• RNA polymerase binds to DNA (in nucleus) form the final mRNA.
and separates the DNA strands
• RNA polymerase then uses one strand of
DNA as a template
• nucleotides are assembled into a strand of
mRNA
The Genetic Code
• Proteins = long chains of amino acids
(polypeptides)
• Polypeptide = combination of any or all
the 20 different amino acids
• properties of proteins are determined by
the order in which different amino acids are
joined together to produce polypeptides.
• The “language” of mRNA instructions is
called the genetic code
• RNA contains four different bases: A, U,
• C, and G
• Letters read “3” at a time = codon
• Codon = a group of three nucleotides on
messenger RNA that specify a
• particular amino acid.
Where does RNA start?
• enzyme will bind only to regions of DNA
known as promoters
• promoters are signals in DNA that indicate
to the enzyme where to bind to make RNA
(“start sequence”).
• Similar signals in DNA cause transcription
to stop when the new RNA molecule is
completed.
FIRST YEAR - FINAL TERM MRS. CECILIA VILLANUEVA 11/2021 - 01/2022
Protein Synthesis
DNA Replication
• DNA must be copied
• The DNA molecule produces 2 IDENTICAL
new complementary strands following the
rules of base pairing: A-T, G-C
• Each strand of the original DNA serves as
a template for the new strand.
• Semiconservative Model:
• Watson and Crick showed: the two strands of
the parental molecule separate, and each
functions as a template for synthesis of a new
complementary strand.
1. Why is replication necessary?
So, both new cells will have the correct DNA
2. When does replication occur?
During interphase (S phase).
3. Describe how replication works.
Enzymes unzip DNA and complementary
nucleotides join each original strand. Transcription & Translation
4. Use the complementary rule to create
the complementary strand:
A---T
G---C
C---G
T---A
A---T
G---C
A---T
G---C
C---G
A---T
, Biochemistry
FIRST YEAR - FINAL TERM MRS. CECILIA VILLANUEVA 11/2021 - 01/2022
Protein Synthesis
• DNA can “unzip” itself and RNA nucleotides • When RNA molecules are formed, both the
match up to the DNA strand. introns and the exons are copied from
• RNA molecules are produced by copying the DNA.
part of the nucleotide sequence of DNA into • introns are cut out of RNA molecules while
a complementary sequence in RNA they are still in the nucleus.
• required enzyme = RNA polymerase • exons are then spliced back together to
• RNA polymerase binds to DNA (in nucleus) form the final mRNA.
and separates the DNA strands
• RNA polymerase then uses one strand of
DNA as a template
• nucleotides are assembled into a strand of
mRNA
The Genetic Code
• Proteins = long chains of amino acids
(polypeptides)
• Polypeptide = combination of any or all
the 20 different amino acids
• properties of proteins are determined by
the order in which different amino acids are
joined together to produce polypeptides.
• The “language” of mRNA instructions is
called the genetic code
• RNA contains four different bases: A, U,
• C, and G
• Letters read “3” at a time = codon
• Codon = a group of three nucleotides on
messenger RNA that specify a
• particular amino acid.
Where does RNA start?
• enzyme will bind only to regions of DNA
known as promoters
• promoters are signals in DNA that indicate
to the enzyme where to bind to make RNA
(“start sequence”).
• Similar signals in DNA cause transcription
to stop when the new RNA molecule is
completed.
