UNIT ___: Translation Name: _____________________

Essential Idea(s):

Information transferred from DNA to mRNA is translated into an amino acid sequence.

2.7.U5: Translation is the synthesis of polypeptides on ribosomes.

Define translation.
State the location of translation in the cell.

2.7.U6: The amino acid sequence of polypeptides is determined by mRNA according to the genetic code.

Outline the role of messenger RNA in translation.

2.7.U7: Codons of three bases on mRNA correspond to one amino acid in a polypeptide.

Define codon, universal and degenerate as related to the genetic code.
Explain how using a 4 letters nucleic acid “language” can code for a “language” of 20 amino acid letters in proteins.

2.7.S1: Use a table of the genetic code to deduce which codons correspond to which amino acids.

Use a genetic code table to deduce the mRNA codon(s) given the name of an amino acid.

2.7.S3: Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence.

Use a genetic code table to determine the amino acid sequence coded for by a given antisense DNA sequence or an mRNA sequence.

2.7.S4: Deducing the DNA base sequence for the mRNA strand.

Deduce the antisense DNA base sequence that was transcribed to produce a given mRNA sequence.

7.3.S1: The use of molecular visualization software to analyse the structure of eukaryotic ribosomes and tRNA molecules.

Describe the structure of the ribosomes, including the small and large subunits and the names and roles of the tRNA binding sites.
Use molecular visualization software to view and identify the small and large subunit and tRNA binding sites of the ribosome.
Outline the structure of tRNA molecules.
Use molecular visualization software to view and identify the anticodon and amino acid binding site of a tRNA.

7.3.U4: Free ribosomes synthesize proteins for use primarily within the cell.

State the difference between free and bound ribosomes.
List destinations of proteins synthesized on free ribosomes.

7.3.U5: Bound ribosomes synthesize proteins primarily for secretion or use in lysosomes.

List destinations of proteins synthesized on bound ribosomes.
Outline how a ribosome becomes bound to the endoplasmic reticulum.

7.3.S2: Identification of polysomes in electron micrographs of prokaryotes and eukaryotes.

Outline the structure of a polysome.
Identify the beginning of an mRNA strand in a micrograph of polysomes.

7.3.U1: Initiation of translation involves assembly of the components that carry out the process.

Outline the process of translation initiation.

7.3.U2: Synthesis of the polypeptide involves a repeated cycle of events.

Outline the process of translation elongation, including codon recognition, bond formation and translocation.
State the direction of movement of the ribosome along the mRNA molecule.

2.7.U8: Translation depends on complementary base-pairing between codons on mRNA and anticodons on tRNA).

Outline the role of complementary base pairing between mRNA and tRNA in translation.

7.3.A1: tRNA-activating enzymes illustrate enzyme-substrate specificity and the role of phosphorylation.

State the role of the tRNA activating enzymes.
Outline the process of attaching an amino acid to tRNA by the tRNA activating enzyme.

7.3.U3: Disassembly of the components follows termination of translation .

Outline the process of translation termination, including the role of the stop codon.

3.1.A1: The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin36358.

State the cause of sickle cell anemia, including the name of differences in the Hb alleles.
State the difference in amino acid sequences in transcription of normal and mutated Hb mRNA.
Outline the consequences of the Hb mutation on the impacted individual.

The Genetic Code

The genetic code is:

Universal

Degenerate

the nitty gritty of …

Translation is the process of building a _________________________ of amino acids, guided by the sequence of ___________________ on the _____________.

In _________________________ cells, the two main steps in protein synthesis occur in separate compartments: transcription in the _________________ and translation in the _____________________. mRNA moves out of the nucleus, to the cytoplasm, through _______________________ in the nuclear membrane.
In ________________________ cells, there is no nucleus, and the chromosome is in direct contact with the cytoplasm, and protein synthesis can begin even while the DNA is still being transcribed.

Structures involved in translation:

Messenger RNA (mRNA):

Transfer RNA (tRNA)

Ribosomes

Amino acids

RIBOSOME Structure	RIBOSOME Location
The ribosomal subunits are constructed of protein and ribosomal RNA (rRNA). Comprises two subunits in which there are grooves where the mRNA strand and polypeptide chain fit in. The subunits form a functional unit only when they attach to a mRNA molecule.	Ribosomes that synthesize proteins for use within the cell are FREELY suspended in the cytoplasm. Ribosomes that synthesize proteins destined for: secretion (by exocytosis) the plasma membrane (e.g., cell surface receptors) lysosomes are BOUND to the endoplasmic reticulum. As the polypeptide is synthesized, it is extruded into the lumen of the ER. Then, before these proteins reach their final destinations, they undergo a series of processing steps in the Golgi apparatus.
RIBOSOME Binding Sites	POLYSOME
The mRNA attaches to the small ribosomal subunit in the “mRNA binding site” The large ribosomal subunit has three tRNA binding sites: The A site The P site The E (exit) site

STEP 1: INITIATION

STEP 2: ELONGATION

Codon Recognition

mRNA codon in the A site

tRNA with complementary ANTI-CODON hydrogen bonds to the codon in the A site

the tRNA brings the appropriate amino acid to the ribosome

Bond formation

The large ribosomal subunit makes a peptide bond (a type of covalent bond) between the amino acid in the A site and the amino acid in the P site.

The mRNA molecule is read and new amino acids are added in the 5’ → 3’ direction

Translocation

The ribosome moves towards the 3’ end of the mRNA strand

Because of the move of the ribosome, there is a shift in the tRNA bindings site (A → P → E)

tRNA leaves the ribosome from the E site

Repeat…

STEP 3: TERMINATION

Adding of amino acids to the polypeptide chain continues until there is a STOP codon on the RNA (UAA, UGA, or UAG)

A “release factor” binds to the stop codon and releases the amino acid chain.

The ribosome dissociates into the two subunits and the amino acid chain can now fold into its secondary, tertiary and/or quaternary structure to become a functional protein