Nucleic Acids and Protein Nucleic Acids and Protein SynthesisSynthesis

CENTRAL DOGMA

• DNA RNA Protein Trait

DNA TO PROTEINS

• DNA is the blueprint for life – it contains your genetic information

• The order of the bases in a segment of DNA (Gene) codes for a particular protein; these proteins then determine your traits

• How do you get from a 4-letter code to an entire organism?

A GENE IS A SEGMENT OF DNA THAT CODES FOR A PROTEIN. NOT ALL DNA CODES FOR PROTEINS.

DNA TO RNA: TRANSCRIPTION

• In the first step of protein synthesis, the code of DNA is transcribed onto a molecule of RNA – this step of the process is known as Transcription

• DNA is too big and too sensitive to leave the nucleus. However, proteins are made in the ribosomes, so the information in DNA must be transferred.

• It will be transferred to a molecule of RNA• RNA is also used because it allows the genetic

information to move from the nucleus (safe) to the cytoplasm (dangerous)

RNARNA

• RNA = Ribonucleic acidRNA = Ribonucleic acid• It is still a nucleic acid – It is still a nucleic acid –

therefore it is made up of therefore it is made up of nucleotides (3 components: nucleotides (3 components: sugar, phosphate group and sugar, phosphate group and nitrogen bases)nitrogen bases)

• It uses ribose as its sugarIt uses ribose as its sugar• Instead of using thymine, it Instead of using thymine, it

uses uracil (A, U, G, C)uses uracil (A, U, G, C)• It is a single strand onlyIt is a single strand only

Types of RNA - mRNATypes of RNA - mRNA

• Messenger RNA (mRNA): single uncoiled chain that Messenger RNA (mRNA): single uncoiled chain that carries the genetic information from the nucleus to the carries the genetic information from the nucleus to the cytosolcytosol

Types of RNA - tRNATypes of RNA - tRNA

Transfer RNA (tRNA): single chain in the formation of a hairpin shape, each piece is bound to a specific amino acid

Types of RNA - rRNATypes of RNA - rRNA

Ribosomal RNA (rRNA): most abundant form, wraps around ribosomal proteins to make up the ribosomes where proteins are made

TranscriptionTranscription

• Process by which genetic information is copied Process by which genetic information is copied (transcribed) from DNA to RNA(transcribed) from DNA to RNA

• RNA polymerase initiates transcription by binding to a RNA polymerase initiates transcription by binding to a specific area of DNA called specific area of DNA called promoterspromoters

• What do you think a promoter is?What do you think a promoter is?• A promoter starts, or promoters the beginning of transcriptionA promoter starts, or promoters the beginning of transcription

• Where the polymerase binds, the DNA strands separate Where the polymerase binds, the DNA strands separate and a template is created upon which RNA is createdand a template is created upon which RNA is created

Transcription (continued)Transcription (continued)

• RNA polymerase attaches to the first nucleotide and RNA polymerase attaches to the first nucleotide and adds on complementary bases using uracil instead of adds on complementary bases using uracil instead of thyminethymine

• Continues until the polymerase reaches the Continues until the polymerase reaches the termination signaltermination signal

• What do you think a termination signal does?What do you think a termination signal does?• Termination signal causes the polymerase to release the DNA Termination signal causes the polymerase to release the DNA

and RNAand RNA

Protein SynthesisProtein Synthesis

• When mRNA is produced it will be used in protein When mRNA is produced it will be used in protein synthesis or the production of proteins synthesis or the production of proteins

• Proteins consist of polypeptides which consist of amino Proteins consist of polypeptides which consist of amino acidsacids

• There are 20 possible amino acidsThere are 20 possible amino acids

Translation: Protein AssemblyTranslation: Protein Assembly

• This process takes the information that was transcribed into mRNA and This process takes the information that was transcribed into mRNA and

translatestranslates it into a protein it into a protein

• It begins when a piece of mRNA attaches to a ribosomeIt begins when a piece of mRNA attaches to a ribosome

• mRNA is “read” by the ribosome. It is read in segments of 3 letters called mRNA is “read” by the ribosome. It is read in segments of 3 letters called

codonscodons

• Each codon codes for a specific amino acid. That amino acid is brought by a Each codon codes for a specific amino acid. That amino acid is brought by a

piece of tRNA which “transfers” amino acids.piece of tRNA which “transfers” amino acids.

• tRNA is also read in segments of 3 letters called tRNA is also read in segments of 3 letters called anticodonsanticodons. The anticodon is . The anticodon is

complementary to the codon found on mRNA ( i.e. if the codon is AUG the complementary to the codon found on mRNA ( i.e. if the codon is AUG the

anticodon is UAC)anticodon is UAC)

• Eventually a Eventually a stopstop codon is reached. They do not code for amino acids. They codon is reached. They do not code for amino acids. They

tell the ribosome to stop adding amino acids. tell the ribosome to stop adding amino acids.

• Many ribosomes may work at once on one piece of mRNAMany ribosomes may work at once on one piece of mRNA

Genetic CodeGenetic Code

• Correlation between Correlation between nucleotides and nucleotides and amino acidsamino acids

• Codon: 3 mRNA Codon: 3 mRNA nucleotides; codes for nucleotides; codes for a specific amino acida specific amino acid

• One codons codes to One codons codes to start (AUG – amino start (AUG – amino acid Methionine) and acid Methionine) and 3 codons can stop 3 codons can stop (UAA, UAG, UGA – no (UAA, UAG, UGA – no amino acids)amino acids)

• If you had a codon If you had a codon AAG, what amino acid AAG, what amino acid would you have?would you have?

• lysinelysine