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Nucleic Acids, DNA Replication,
and Protein Synthesis
November 3, 2007
Bio099
Timberlake Chapter 17
Martinin Pages 54-55
Nucleic Acids: The Big Picture
Two Types of Nucleic Acids
Two Types
1.
DNA
Deoxyribonucleic acid
Two Types of Nucleic Acids
Two Types
1.
DNA
Deoxyribonucleic acid
2.
RNA
Ribonucleic acid
Nucleotide
The monomer of nucleic acids
Molecular Components of
the nucleotide
1. Pentose sugar
DNA
RNA
Molecular Components of
the nucleotide
1. Pentose sugar
2. Phosphate group
Molecular Components of
the nucleotide
1. Pentose sugar
2. Phosphate group
3. Nitrogenous bases
purine
pyrimidine
Nitrogenous Bases
BASES OF DNA
BASES OF RNA
Nucleoside
Primary Structure of Nucleic Acids
• Nucleotides are
bound together to
form nucleic acids.
Primary Structure of Nucleic Acids
• Nucleotides are
bound together to
form nucleic acids.
– The sequence of
bases is like an
instruction manual that
can be read by the
cell.
Secondary Structure of
Nucleic Acids
• DNA:
The Double Helix
The vertical blue strand
represents the sugar and
phosphate group and the inner
horizontal bands represent the
nitrogenous bases
Secondary Structure of
Nucleic Acids
• DNA:
The Double Helix
– Complementary base
pairs
Secondary Structure of
Nucleic Acids
• DNA:
The Double Helix
– Complementary base
pairs
– Helical
Secondary Structure of
Nucleic Acids
• RNA:
Single stranded, but loopy in structure
Review
• What are the 2 types of nucleic acids?
Review
• What are the 2 types of nucleic acids?
• RNA and DNA
Review
• What are the 2 types of nucleic acids?
• RNA and DNA
• What molecules makes up the “backbone”
of a nucleic acid?
Review
• What are the 2 types of nucleic acids?
• RNA and DNA
• What molecules makes up the “backbone”
of a nucleic acid?
• phosphate and sugar
Review
• What are the 2 types of nucleic acids?
• RNA and DNA
• What molecules makes up the “backbone”
of a nucleic acid?
• phosphate and sugar
• What is one difference between RNA and
DNA?
Review
• What are the 2 types of nucleic acids?
• RNA and DNA
• What molecules makes up the “backbone”
of a nucleic acid?
• phosphate and sugar
• What is one difference between RNA and
DNA?
• secondary structure (double stranded helix vs.
single stranded)
• nitrogenous bases (RNA uses uracil instead of
thyamine)
DNA Replication
• Each time a cell
divides, its entire
genome must be
copied and passed on
to the new cell.
DNA Replication
• 1 double helix replicates
to give 2 new double
helixes
DNA Replication
• 1 double helix replicates
to give 2 new double
helixes
• The 2 new DNA
molecules are made of 1
OLD and 1 NEW
polynucleotide strands
The Steps of DNA Replication
1.
The two DNA strands are unwound with the help of the
enzyme HELICASE which facilitates the breaking of
the chemical bonds between the molecules.
The Steps of DNA Replication
2.
DNA POLYMERASE helps to form bonds between the
nucleotides of the newly formed strand.
Review
• What must happen before a cell divides?
Review
• What must happen before a cell divides?
• DNA replication
Review
• What must happen before a cell divides?
• DNA replication
• What enzyme helps to unwind the DNA so
it can be copied?
Review
• What must happen before a cell divides?
• DNA replication
• What enzyme helps to unwind the DNA so
it can be copied?
• Helicase
Protein Synthesis
The Big Picture
DNA
(instructions)
RNA
(copy of instructions)
Protein
(result of following instructions)
Protein Synthesis requires
3 types of RNA
DNA
RNA
Protein
Three Types of RNA
1. messenger RNA (mRNA)

copy of a gene (DNA)

leaves nucleus
to carry genetic
information to
the ribosome for
protein synthesis
Three Types of RNA
2. ribosomal RNA (rRNA)

part of the ribosome
Three Types of RNA
3. transfer RNA (tRNA)
•
•
•
transfers the amino acids
to the ribosome for
protein synthesis.
Steps of Protein Synthesis
1. Transcription of the genetic material.
•
making the mRNA.
Steps of Protein Synthesis
1. Transcription of the genetic material.
•
making the mRNA.
Why is it a
good idea to
make a copy
of the DNA
to leave the
nucleus?
Steps of Protein Synthesis
2. The mRNA travels to the cytoplasm.
Steps of Protein Synthesis
3. Translation of the mRNA
•
The word translation is used because the language is changing
from nucleic acids to amino acids.
•
A genetic code is used by the cell to translate the genetic material
(mRNA) into a protein
•
3 nucleotides of mRNA make a codon
that translates to a specific amino acid,
or a start or stop message during
protein synthesis.
Steps of Protein Synthesis
3. Translation of the mRNA is initiated with
a start codon.
Steps of Protein Synthesis
4. Translation of the genetic material
continues and the polypeptide gets
longer.
Steps of Protein Synthesis
5. Termination occurs when a stop codon is
reached.
Review
• What is transcription?
Review
• What is transcription?
• copying a gene (DNA) into mRNA
Review
• What is transcription?
• copying a gene (DNA) into mRNA
• _________ is the process that creates a
protein from a strand of mRNA.
Review
• What is transcription?
• copying a gene (DNA) into mRNA
• _________ is the process that creates a
protein from a strand of mRNA.
• translation
Review
• What is transcription?
• copying a gene (DNA) into mRNA
• _________ is the process that creates a
protein from a strand of mRNA.
• translation
• What type of mRNA carries the amino
acids to the ribosome during translation?
Review
• What is transcription?
• copying a gene (DNA) into mRNA
• _________ is the process that creates a
protein from a strand of mRNA.
• translation
• What type of mRNA carries the amino
acids to the ribosome during translation?
• transfer (t) RNA
Genetic Mutations
• Mutations are changes in the sequence of nucleotides in
DNA.
G
U
G
A
U
C
Genetic Mutations
• Mutations are changes in the sequence of nucleotides in
DNA.
G
U
G
A
U
How would this mutation impact protein translation?
C
Genetic Mutations
• Mutations are changes in the sequence of nucleotides in
DNA.
G
U
G
A
U
C
• Mutations within a gene can alter the sequence of amino
acids in a protein causing changes, or lack of protein
function.
Types of Mutations
• Substitution
Types of Mutations
• Substitution
Types of Mutations
• Frameshift
Genetic Mutations and Disease
• A mutation in the gene that encodes the
protein leptin leads to marked obesity in
rodents and humans.
Genetic Diseases
• For more examples of genetic diseases
caused by mutations see Timberlake
Table 17.5