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 DNA Deoxyribonucleic acid

Two Types of Nucleic Acids DNA Deoxyribonucleic acid RNA Ribonucleic acid

Nucleotide The monomer of nucleic acids

Molecular Components of the nucleotide Pentose sugar DNA RNA

Molecular Components of the nucleotide Pentose sugar Phosphate group

Molecular Components of the nucleotide Pentose sugar Phosphate group 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 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 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 messenger RNA (mRNA) copy of a gene (DNA) leaves nucleus to carry genetic information to the ribosome for protein synthesis

Three Types of RNA ribosomal RNA (rRNA) part of the ribosome

Three Types of RNA transfer RNA (tRNA) transfers the amino acids to the ribosome for protein synthesis.

Steps of Protein Synthesis Transcription of the genetic material. making the mRNA.

Steps of Protein Synthesis 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 The mRNA travels to the cytoplasm.

Steps of Protein Synthesis 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 Translation of the mRNA is initiated with a start codon.

Steps of Protein Synthesis Translation of the genetic material continues and the polypeptide gets longer.

Steps of Protein Synthesis 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. U G A U G C

How would this mutation impact protein translation? Genetic Mutations Mutations are changes in the sequence of nucleotides in DNA. U G A U G C How would this mutation impact protein translation?

Genetic Mutations 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. U G A U G 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