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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. DNADeoxyribonucleic acid
Two Types of Nucleic Acids
Two Types
1. DNADeoxyribonucleic acid
2. RNA
Ribonucleic acid
NucleotideThe 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 basespurine 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 Replication1. 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 Replication2. 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 SynthesisThe 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
• Mutations are changes in the sequence of nucleotides in DNA.
Genetic Mutations
UG A
UG
C
• Mutations are changes in the sequence of nucleotides in DNA.
Genetic Mutations
UG A
UG
C
How would this mutation impact protein translation?
• Mutations are changes in the sequence of nucleotides in DNA.
• Mutations within a gene can alter the sequence of amino acids in a protein causing changes, or lack of protein function.
Genetic Mutations
UG A
UG
C
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
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