Bio Unit 5A Translation

Front 1

What is the genetic code?

Back 1

relationship between sequence of nucleotides in DNA/RNA and sequence of amino acids in a protein

Front 2

How many possible codons are there?

Back 2

-64 (4 power of 3) possible codons yet only 20 amino acids (AAs)
-all AAs except methionine (Met) and tryptophan (Trp) are specified by more than one codon

Front 3

Even though there are many codons that specify an amino acid, one codon NEVER specifies more than one
amino acid. (T/F)

Back 3

True

Front 4

Genetic code is almost universal (T/F)

Back 4

True

Front 5

_______ or _______ of bases that shift the reading frame can lead to novel proteins that are beneficial, or they can be disastrous.

Back 5

Loss, gain

Front 6

How does an mRNA codon specify an amino acid?

Back 6

An adapter molecule holds the amino acids in place while interacting directly and specifically with a codon in mRNA

Front 7

What is an adapter molecule?

Back 7

tRNA!

Front 8

There's a different aminoacyl tRNA synthetase and one or more tRNAs for each amino acid (T/F)

Back 8

true

Front 9

What do tRNAs look like?

Back 9

Clover leaf

Front 10

Where in the tRNA are the binding sites for AAs?

Back 10

CCA sequence at 3’ end

Front 11

How does tRNA become aminoacyl tRNA?

Back 11

-ATP and AA bind to aminoacyl tRNA synthase (enzyme)
-2 phosphorous bonds leave the ATP (making it AMP) which now attaches to the AA
-Once the AMP and AA bind together, the AA becomes activated
-tRNA specific to the AA in the enzyme binds to the active site
-The AA and tRNA will bind together, and AMP will fall off
-aminoacyl tRNA leaves enzyme and is ready for translation

Front 12

What is the wobble hypothesis?

Back 12

Proposes that the anticodon of tRNAs can still bind successfully to a codon (on mRNA) whose third position requires a nonstandard base pairing

This explains how one tRNA is able to base pair with more than one type of codon

Front 13

What are the components of a ribosome (eukaryotic)?

Back 13

-small subunit
-large subunit

Front 14

Translation begins when?

Back 14

The anticodon of a ‘charged’ tRNA binds to a codon in mRNA

Front 15

Translation ends when?

Back 15

That amino acid forms a peptide bond with growing chain

Front 16

Once translation is ongoing, ______ of the 3 binding sites within the ribosome are occupied by a tRNA at any given time.

Back 16

2

Front 17

What are the 4 sites within a ribosome?

Back 17

A site- acceptor site
P site- where peptide bonds form
E site- where tRNAs no longer bound to an amino acid leaves

Front 18

Which subunit moves first during the process of translation (translocates)?

Back 18

Large

Front 19

Are ribosomes ribozymes?

Back 19

Yes

Front 20

What initiates translation?

Back 20

The initiator tRNA loaded with met binds to small ribosomal subunit (loaded with proteins known as translation initiator factors); binds tightly to P site of small ribosomal subunit (only initiator tRNA can do this)

Front 21

What happens after the initiation of translation?

Back 21

Step 2: the initiator tRNA loaded with an AA moves along the mRNA with the small subunit in search for the first AUG

Step 3: when AUG is found, the initiation factors dissociate and the large ribosomal subunit binds

Step 4: next charged tRNA can move into A site, and strand synthesis can begin

Front 22

What terminates translation?

Back 22

The presence of a STOP codon in the mRNA

Front 23

What happens when a stop codon reaches the A site?

Back 23

The stop codon will bind a release factor that alters catalytic activity, causing addition of a water rather then forming a peptide bond. Polypeptide chain is finished, and subunits fall off the mRNA

Front 24

Proteins are made on?

Back 24

Polyribosomes

Front 25

How can you speed up the process of translation of an mRNA?

Back 25

If another ribosome hops on the mRNA and starts translating the same message as soon as the first one is out of the way. This is common in both bacteria and eukaryotes

Front 26

When do proteins fold?

Back 26

Begins during translation, long before termination and disassembly of ribosomes

Front 27

Does folding of proteins occur ‘spontaneously’?

Back 27

Yes

Front 28

What are molecular chaperones?

Back 28

They bind to ribosome near ‘tunnel’ where growing peptide exits and helps protein develop its appropriate structure

Front 29

What are Post-Translational Modifications (PTMs)?

Back 29

Chemical modification of protein structure which generally involves addition of functional groups/small molecules to protein

Front 30

Post-translational modifications increase protein diversity (T/F)

Back 30

True

Front 31

Overview of Protein Synthesis in Eukaryotes

Back 31