Transcription and Translation

Question 1

What organelle is the site of ribosome synthesis?

Answer 1

Nucleolus

Question 2

In what form does the information copied from a gene take?

Answer 2

mRNA (messenger RNA)

Question 3

What ends do the G cap (guanosine cap) and Poly A tail get added to?

Answer 3

5’ end - G cap
3’ end - Poly A tail

Question 4

What are introns and what are exons?

Answer 4

Introns are non-coding regions of the sequence that is removed from the immature mRNA strand

Exons are coding regions that are spliced together to form mature mRNA

Question 5

What is transcription?

Answer 5

The process in which DNA is transcribed into mRNA

Question 6

What is translation?

Answer 6

The process in which mRNA is translated into protein

Question 7

What occurs during translation? All steps

Answer 7

1. Binding of small ribosomal subunit to mRNA

translation begins with the small ribosomal unit binding to an mRNA strand and an initiator tRNA carrying the start codon AUG methionine binds to the mRNA strand

2. Formation of functional ribosome

the small and large ribosomal units join together and enclose the mRNA and tRNA. the large ribosomal unit has 3 sites for tRNA binding, EPA

E - EXIT
P - POLYPEPTIDE BUILDING
A - ARRIVAL

3. Formation of peptide bond

a second tRNA then arrives at the site of the ribosome, carrying amino acid 2. its anti codon binds to the second codon of the mRNA strand and ribosomal enzymes now remove amino acid 1 from the first tRNA in the P site and attach it to amino acid 2 with a peptide bond

4. Extension of Polypeptide

the ribosome now moves one codon farther along the length of the mRNA strand. a third tRNA arrives at the A site, bearing amino acid 3. the first tRNA then detaches from the E of the ribosome and reenters the cytosol where it will pick up another amino acid and repeat the process

5. Completion and release of polypeptide

elongation continues until the ribosome reaches a stop codon and the mRNA strand is freed