Protein synthesis

What do ribosomes create?

Proteins

Name the two main stages of the production of proteins from the DNA code

Transcription and translation

Give a rough description of transcription

One gene of the DNA is copied into mRNA

Give a rough description of translation

• mRNA joins with a ribosome

• corresponding tRNA molecules bring the specific amino acid the codon codes for

What is the first step in the process of transcription?

• Hydrogen bonds between DNA bases break catalyzed by DNA helicase.

• Causing DNA double helix to separate and expose template strand

What occurs in transcription after the template strand is exposed?

Free RNA nucleotides align by complementary base pairing to the exposed bases on the DNA template strand

How many DNA strands act as a template for RNA formation?

1

Which DNA base pairs with Uracil in RNA?

Adenine

What occurs in transcription after the free RNA nucleotides align by complementary base pairing?

• Enzyme RNA polymerase catalyses the condensation reaction of joining adjacent RNA nucleotides together

What occurs in transcription after the condensation reaction has joined adjacent RNA nucleotides together?

• Phosphodiester bonds form between adjacent RNA nucleotides

• Creating the sugar-phosphate backbone of RNA strand

What occurs in transcription once the mRNA has been copied?

mRNA is modified and leaves the nucleus through the nuclear envelope pores.

What is pre-mRNA and which kind of cell is it found in?

• The initial RNA strand

• Eukaryotic cells

What process does the pre-mRNA undergo in eukaryotic cells? Describe it

• Splicing,

• Where introns are removed and exons are joined together to form mRNA :)

Does prokaryotic DNA contain introns?

Nope :p

Compare transcription in eukaryotic cells to transcription in prokaryotic cells.

• Pre-mRNA in eukaryotic cells undergoes splicing to remove introns and join exons together to form mRNA

• Transcription in prokaryotic organisms directly results in the production of a finished mRNA molecule BECAUSE prokaryotic DNA does not contain introns.

What is the first stage of translation?

• mRNA attaches to a ribosome in the cytoplasm after leaving the nucleus

How does the ribosome read the sequence of codons on the mRNA?

One at a time

What occurs in translation after the ribosome has read the codon sequence on mRNA?

• The codon on mRNA binds to a molecule of tRNA .

• with an anti-codon complementary to the codon on mRNA by complementary base pairing.

Where does complementary base pairing occur in translation?

• Occurs first at start codon

• Molecule of tRNA (with anti-codon complementary to the bases on mRNA) binds to that mRNA.

What determines which specific amino acid each tRNA molecule carries?

The anti-codon on the tRNA molecule.

What occurs in translation after the tRNA binds to the mRNA?

• By using a peptide bond,

• The ribosome joins the amino acid carried by the tRNA molecules

1) What is required for the attachment of amino acids to tRNA molecules? (before they join the ribosomes)

2) What does this form between the amino acids?

• ATP as it requires energy

• Peptide bonds form between the amino acids

What occurs in translation after the amino acids are attached to tRNA molecules via ATP?

• Ribosome moves along mRNA to next codon

• Process repeats; new tRNA molecules bind which bring along more amino acids

What occurs in translation when the ribosome has reached the stop codon?

• No tRNA binds to stop codon

• Polypeptide releases from ribosome

What occurs post-translation after the polypeptide chain has been created?

• Polypeptide chain enters Golgi body for folding and modification.