Nucleic Acids, DNA Replication, and Protein Synthesis November 3, 2007 Bio099 Timberlake Chapter 17 Martinin Pages 54-55.

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