Protein synthesis: OverviewProtein synthesis: OverviewSection 5.2, page 237

DefinitionsDefinitionsGene – A sequence of nucleotides in DNA that

performs a specific function, such as coding for a particular protein

Proteins – Complex macromolecules composed of one or more polypeptide chains◦ Functions: hormones, enzymes, membrane structure

DNA is in the nucleus

Ribosomes (which synthesize protein) are in the cytoplasmHow does the ribosome synthesize the

protein, without having access to the DNA?

The central dogma of molecular biologyThe central dogma of molecular biology

RNA is an intermediate messenger molecule

The central dogma involves two steps:

1.Transcription2.Translation

Transcription:The information in DNA

is transcribed into a complementary mRNA message.

Translation:The ribosomes read the information in RNA and translate it, in order to synthesize a protein.

RNA: A nucleic acidRNA: A nucleic acid

uracil (U) in RNA pairs with the adenine (A) in DNA

Checkpoint:Checkpoint:A coding portion of DNA is shown below.What is the sequence of complementary

RNA that will be transcribed?

DNA: 3’- T A C T T A C G A T C G -5’RNA: 5’ - -3’

Classes of RNAClasses of RNAThree types:

1.messenger RNA (mRNA)2.transfer RNA (tRNA)3.ribosomal RNA (rRNA)

HomeworkHomework

Page 241 #1-5