mRNA

Question 1

what is the role of mRNA?

Answer 1

mRNA carries the genetic information from the nucleus to the cytoplasm for the ribosomes to translate the genetic information into the amino acid sequence of a polypeptide chain, as DNA molecules are too large to pass through the nuclear pores in the nucleus

Question 2

which type of organism synthesizes pre-mRNA in the nucleus upon transcription of the gene?

Answer 2

eukaryotes

Question 3

what must be done to pre-mRNA before they can be transported out of the nucleus?

Answer 3

the pre-mRNA must undergo post-transcriptional modification to form mature mRNA before it can be transported out of the nucleus

Question 4

how does having a smaller size than DNA allow mRNA to perform its role?

Answer 4

• having a smaller size than DNA (structural feature)
• allows mRNA to move out of the nucleus via nuclear pores, and hence carry genetic information to the ribosomes in the cytoplasm for translation (significance to its role)

Question 5

how does having a sequence of codons complementary to the bases on the DNA template strand from which it is transcribed significant to the role of mRNA?

Answer 5

• as each codon codes for 1 amino acid, the codon sequence on the mRNA specify the amino acid sequence of the polypeptide chain (significance to its role)

Question 6

how does being single-stranded enable mRNA to carry out its role?

Answer 6

• being single-stranded (structural feature)
• allows aminoacyl-tRNA complexes with complementary anti-codons to base pair with codons on the mRNA during translation (significance to its role)

Question 7

how does the presence of a start codon, AUG, enable mRNA to carry out its role?

Answer 7

• AUG codes for the 1st amino acid, methionine, for all polypeptides
• is it also the site where translation is initiated

Question 8

why is the start codon the site where translation is initiated?

Answer 8

this is because the start codon is the recognition site for binding of the large ribosomal subunit to complete the formation of the translation initiation complex

Question 9

how does the presence of stop codons, UAG, UAA, UGA, enable mRNA to carry out its role?

Answer 9

• the stop codons do not code for any amino acids

- hence is the site where translation is terminated

Question 10

why is any of the stop codons the site where translation is terminated?

Answer 10

this is because the stop codon is the recognition site for binding of a release factor involved in the release of the polypeptide chain from the ribosome