3.10 Protein Synthesis: TRANSCRIPTION/SPLICING

Question 1

What are the names of the 2 stages of protein synthesis?

Answer 1

Transcription and translation

Question 2

Where is DNA contained?

Answer 2

Within a double membrane, the nuclear envelope, which encloses the nucleus and protects the DNA from being damaged in the cytoplasm

Question 3

Describe the stages of transcription in protein synthesis.

Answer 3

-DNA helicase unwinds a gene by breaking hydrogen bonds between complementary bases
-Free RNA nucleotides pair up with exposed anti-sense strand bases by complementary base pairing (A->U, T->A, C<->G)
-RNA polymerase joins up RNA nucleotides by forming phosphodiester bonds, making mRNA
-mRNA leaves nucleus through the nuclear pore to travel to ribosomes for translation.

Question 4

Why does mRNA have to be formed (instead of simply duplicating DNA)?

Answer 4

Because DNA is too large to exit the nucleus, and RNA is small enough to exit.

Question 5

What is an exon?

Answer 5

A part of the DNA that codes for proteins

Question 6

What is an intron?

Answer 6

A non-coding part of the DNA

Question 7

What type of cells contain exons and introns?

Bacteria, eukaryotic..?

Answer 7

Eukaryotic cells

Question 8

What is the name of the process where introns are removed by enzymes from mRNA?

Answer 8

Splicing

Question 9

What does mRNA stand for?

Answer 9

Messenger Ribonucleic Acid

Question 10

Describe the process of splicing. in the context of protein synthesis.

Answer 10

-During transcription, mRNA strands are processed before exiting the nucleus
-Introns are cut out of the mRNA by spliceosome, and exons are joined together
-Newly formed mRNA detaches from the DNA and leaves the nucleus

Question 11

What is the name of the enzyme that cuts introns from mRNA?

Answer 11

Spliceosome

Question 12

What enzyme catalyses the reaction of amino acids being joined by a peptide bond?

Answer 12

Peptidyl transferase