Central Dogma of BiologyFrom DNA to Protein

Overview:

DNA---------------------> RNA--------------------> Proteintranscription translation

Genes code for proteins

RNA

• RNA is a nucleic acid. • Different than DNA in three ways.1. RNA is single stranded2. Sugar in RNA is ribose3. RNA does not contain nitrogenous base

thymine but instead contains nitrogenous base uracil (U)

RNA

• Three types of RNA1. messenger RNA (mRNA)Brings the instructions from the nucleus to the cytoplasm to make proteins2) . ribosomal RNA (rRNA)Binds to the mRNA and uses the instructions to bind amino acids to make a protein. 3. transfer RNA (tRNA) delivers amino acids to the ribosome to be assembled into a protein.

How proteins are made

• TranscriptionEnzymes make an RNA copy of a portion of a DNA strand in the process called transcription.*DNA To RNA (mRNA)Everything from DNA is copied but not all is needed.

How proteins are made

• RNA ProcessingNot all the nucleotides in the DNA of eukaryotic cells carry instructions or code for making proteins. Long noncoding nucleotide sequences are called introns.Coding nucleotide sequences are called exons.When mRNA is transcribed from DNA both introns and exons are copied. The segments of introns on mRNA are removed and only the exons are put back together and the new mRNA leaves the nucleus and travels to the ribosome.

The Genetic Code

The strand of mRNA transcribed from DNA acts as a genetic message ( the complete information for building of a protein)

The message on mRNA is broken into sections of three nitrogenous bases called a codon. Each codon codes for one amino acid. Ex. UUU results in the amino acid phenylalanine being placed in a protein.

The genetic code

There are a total of 64 possible combination sequence of three bases. Not all code for a protein. Codon AUG is a start codonCondon UAA is the stop codon indicating that the protein chain ends at that point.

Translation: From mRNA to Protein

Translation is the process of converting the information in a sequence of nitrogenous bases in mRNA.Translation takes place at the ribosome in the cytoplasm.

• The role of transfer RNA (tRNA)• Each tRNA molecule attaches to only on type

of amino acid.

Translation: From mRNA to Protein

The tRNA has a section that is called the anticodon. The anticodon on the tRNA pairs up with the codon on the mRNA. The tRNA has a specific amino acid. Another tRNA with the anticodon for the next codon comes and then the two amino acids bonded together by a peptide bond. The amino acids breaks free from the tRNA and the process continues and the protein gets larger and stops until it reaches a stop codon.

Translation: mRNA to Protein• The amino acids fold, twist into a 3D structure and then you have a

protein.