Protein Synthesis

RNA carries DNA’s instructions. Information flows in one direction from to to .

Protein Synthesis involves 2 processes: replication transcription translation RNA is a link between DNA and proteins.

3.5.1 – Compare the structure of RNA and DNA. RNA differs from DNA in three major ways. Sugar: RNA has a DNA has a Bases: RNA has instead of Number of strands: RNA is DNA is

Three types of RNA messenger RNA (mRNA) – mRNA nucleotides are read in groups of three called each codon codes for a

mRNA

Three types of RNA transfer RNA (tRNA) – Each tRNA carries a specific type of amino acid Each tRNA can (sequence of three bases that associates with the codon by base pairing)

If the mRNA codon was AUG, what would the anticodon be? tRNA If the mRNA codon was AUG, what would the anticodon be?

Three types of RNA ribosomal RNA (rRNA) –

Overview of Protein Synthesis During transcription, one DNA strand, (template strand), provides a template for making an mRNA molecule. Complementary mRNA molecule is made using base-pairing rules, except uracil pairs with adenine. If the DNA template was ATG, which mRNA bases would pair with it?

Overview of Protein Synthesis During translation, blocks of three nucleotides (codons) are decoded into a sequence of amino acids.

Transcription is catalyzed by 3.5.2 – Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase Transcription Takes place in the Copies Transcription is catalyzed by start site nucleotides RNA polymerase

RNA polymerase moves along the DNA 3.5.2 – Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase Nucleotides pair with one strand of the DNA. RNA polymerase The DNA helix winds again as the gene is transcribed. DNA RNA polymerase moves along the DNA

Ex. mRNA is a complementary copy of DNA – travels out of nucleus to 3.5.2 – Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase mRNA is a complementary copy of DNA – travels out of nucleus to Ex. DNA A T C C G G A A T C G G T A A A T T mRNA

The mRNA strand detaches from the DNA once the gene is transcribed 3.5.2 – Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase The mRNA strand detaches from the DNA once the gene is transcribed RNA

3.5.4 – Explain the process of translation leading to polypeptide formation Transfer RNA (tRNA) transfers amino acids from the cytoplasm’s pool to a ribosome. The ribosome .

Amino acids are coded by Translation 3.5.3 – Describe the genetic code in terms of codons composed of triplets of bases. Amino acids are coded by Translation A is a sequence of three nucleotides on mRNA that codes for a particular amino acid codon for methionine (Met) leucine (Leu)

Regardless of the organism, 3.5.4 – Explain the process of translation leading to polypeptide formation Amino acids are put in a specific order to – the order of the amino acids is determined by the Regardless of the organism,

Ribosomes consist of two subunits. 3.5.4 – Explain the process of translation leading to polypeptide formation Ribosomes consist of two subunits. The large subunit has . The small subunit

How does the ribosome “read” and translate the mRNA? 3.5.4 – Explain the process of translation leading to polypeptide formation How does the ribosome “read” and translate the mRNA? Step1: A special initiator tRNA attaches to the The large subunit of the ribosome closes over the tRNA In all organisms, protein synthesis begins with the codon (codes for )

Step 2: The polypeptide chain grows as new tRNA molecules move into position by complementary base pairing of their anticodon with the next codon on the mRNA

Ribosome links amino acids together by Translation continues until ribosome reaches a Codons that do not code for an amino acid Indicates that

The genetic code matches each codon to its amino acid The genetic code is (redundant) More than one codon codes for CODON AMINO ACID AGU AGC GGU

Exceptions…are all protein made of one polypeptide??? 3.5.5 – Discuss the relationship between one gene and one polypeptide The genetic code – the sequence of nucleotides in DNA – is ultimately translated into the sequence of amino acids in proteins – gene expression In general, (can be structural or enzymatic) – one-gene, one-protein hypothesis Exceptions…are all protein made of one polypeptide???