Chapter 17: Gene Expression Part 2

Question 1

tRNA

Answer 1

Transfer RNA. Transfer amino acids in the cytoplasm to polypeptides in a ribosome. Very picky with their aminos

Question 2

anticodon

Answer 2

Base pair on tRNA with complementary codon on mRNA, float around in the cytoplasm to pick up their amino acid

Question 3

aminoacyl-tRNA synthestase

Answer 3

Enzyme catalyzes the covalent bond of amino specific-tRNA with it’s amino acid

Question 4

Start codon

Answer 4

always AUG, on all mRNA, starts translation

Question 5

Initiation Factors

Answer 5

proteins that bring in the large subunit to complete the translation initiation, builds a translation assembly

Question 6

Elongation Factors

Answer 6

proteins that help bind the aminos to each other at the c-terminus, forming the polypeptide chain

Question 7

Stop Codon

Answer 7

3 different ones that stop the translation of mRNA

Question 8

Release Factor

Answer 8

Protein causes the addition of a water molecule instead of an amino acid

Question 9

Differentiate among the words triplet, codon, and anti-codon

Answer 9

Triplet is 3 nucleotide sequence on DNA. Transcribed to a mRNA in a codon. That codon is read by tRNA, with an anticodon (the complement to the codon found on mRNA).

Question 10

Accurate translation requires 2 steps. Briefly describe each.

Answer 10

Correct match between transfer RNA and amino acid in the cytoplasm, done by aminoacyl-tRNA synthestase. The amino acid (ex: tyr) and the tyr-tRNA bind to Tyrosyl-tRNA synthetase, which catalyzes the bond to it’s specific tRNA

A correct match between the tRNA anticodon and an mRNA codon

Question 11

What are the 3 binding sites on a ribosome for tRNA? Define each.

Answer 11

P: Peptidyl-tRNA site, carries growing polypeptide chain
A: holds the tRNA that carries the next amino acid to be added to the chain
E: Exit site, discharge tRNA leave the ribosomes

Question 12

Describe/explain the 3 steps of translation

Answer 12

Initiation: small ribosomal subunit binds with mRNA and a special initiator tRNA, the subunit moves along the mRNA til the start codon. Initiation factors bring the large subunit that completes the translation initiation

Elongation: Aminos added to the c-terminus of the growing amino acid chain/polypeptide, continues til a stop codon reaches the A site

Termination: Once elongation ends, the a site accepts a “release factor”, which adds water instead of an amino, releasing the polypeptide (mRNA) from the Ribosome, ending translation and making the assembly come apart

Question 13

What are the 3 steps of the elongation phase of translation?

Answer 13

Codon recognition. Peptide bond formation is the bond between aminos and c-terminus. Translocation movement of aminos from one tRNA to the next.