Week 20- Translation and Recombinant DNA (and workshop because why not?)

Question 1

What is a codon?

Answer 1

A codon is a nucleotide triplet that encodes for a specific amino acid

Question 2

Why is the genetic code redundant?

Answer 2

Because some amino acid are encoded by more than one codon

Question 3

Why is the genetic code non ambiguous?

Answer 3

Because one codon can specify only one amino acid

Question 4

What are the three functions of tRNA?

Answer 4

1) tRNA binds to a particular amino acid to become charged 2)tRNA binds to a mRNA at a region called the anticodon. 3) tRNA interact with ribosomes

Question 5

What is a ribosome?

Answer 5

A molecule that contain RNA and it’s composed of two subunits.

Question 6

What are the two subunits of the ribosome?

Answer 6

Large subunit and Small subunit

Question 7

Describe the large subunit

Answer 7

Consists of 3 different molecules of rRNA and 49 different proteins.

Question 8

Describe small subunit:

Answer 8

Consists of 1 rRNA molecule and 33 different proteins.

Question 9

Describe A site:

Answer 9

A stands for amynoacil and is where the charged tRNA anticodon binds to the mRNA codon.

Question 10

Describe the P site:

Answer 10

P stand for peptidyl and is where the tRNA adds its amino acid to the polypeptide chain.

Question 11

Describe E site:

Answer 11

E stands for exit. After tRNA gave up its amino acids it is released from this site.

Question 12

What are the three phases of translation?

Answer 12

1) Initiation 2) Elongation 3) Termination

Question 13

Describe Initiation of translation:

Answer 13

1) The initiation complex is formed. 2) The anticodon and the start codon bind via complementary base pairing. 3) The large subunit join the complex

Question 14

Describe Elongation of translation:

Answer 14

1) a charged tRNA whose anticodon is complemenary to the second codon of mRNA enters the A site. 2) The large subunits catalyze the peptydil transferase activity. 3)The first tRNA releases its amino acid chain and moves to the E site where it dissociate from the ribosome. 4) The next tRNA is shifter to the P-Site and the ribosome moves one codon along.

Question 15

Describe termination of translation:

Answer 15

A stop codon enters the A site, it doesn’t corresponds to any amino acid and they don-t bind to any tRNA. Instead, they bind a protein release factor that allows the hydrolisis of the bond between the polypeptide chain and the tRNA in the P-site.

Question 16

What are the two reaction that form the peptidyl transferase activity?

Answer 16

1) It breaks the bond between tRNA and its amino acid in the P-site. 2) It catalyze the formation of a peptide bond between the amino acids on the P and on the A sites.

Question 17

What are polyribosome:

Answer 17

Several ribosomes that work simultaneously on the same mRNA translating and producing multiple polypeptide at the same time.

Question 18

What are the two possibile paths that a protein can take when it’s synthesised?

Answer 18

It can either complete the trnalsation and being release to an organelle (or remain in the cytosol) or stop translation, go to the endoplasmic reticulum and finish synthesis there.

Question 19

What are the three different post-translational process

Answer 19

1) Glycolisation 2) Proteolysis 3) Phosphorilation

Question 20

Describe Proteolysis:

Answer 20

Cutting of a polypetide chain catalysed by protease.

Question 21

Describe Glycolisation:

Answer 21

Additioon of a sugar to protein to make glycoprotein.

Question 22

Describe Phosporilation:

Answer 22

Addition of a phosphate group to protein catalysed by kinases.

Question 23

What are restriction endonucleases?

Answer 23

Enyzmes that cut DNA at specific sequences and create sticky ends.

Question 24

Describe DNA ligase:

Answer 24

Enzyme that join the 5’ end of one polynucleotide to the 3’ end of another polynucleotide.

Question 25

What is recombinant DNA?

Answer 25

A DNA molecule that has been made in laboratory using at least different sources of DNA.

Question 26

What are plasmids?

Answer 26

Small circualr DNA molecules that replicate autonomously in many prokaryotes.

Question 27

What are the three characteristics of plasmids?

Answer 27

1) An origin of replication that allow the plasmid to reproduce. 2) Selectable marker genes (usually antibiotics). 3) Unique restriction endonucleases sites for the insertion of a DNA fragment.

Question 28

What are homopolymers?

Answer 28

Nucleic acids or polypeptides that contain a single type of subunit

Question 29

What are heteropolymers?

Answer 29

Nucleic acids or polypeptide that contain more tha one class of subunits