8.3 Structures of ribonucleic acid

Question 1

How does genetic information for the synthesis of proteins leave the nucleus?

Answer 1

It is transcribed onto a single-stranded molecule of RNA.

Question 2

What is the role of messenger RNA?

Answer 2

To transfer the DNA code from the nucleus to the cytoplasm.

• small enough to enter and leave the nucleus through the nuclear pores
• it travels to the cytoplasm where the coded information it contains is used to synthesise proteins.

Question 3

What is a genome?

Answer 3

The complete set of genes in a cell, including in the mitochondria/chloroplasts.

Question 4

What is a proteome?

Answer 4

The full range of proteins produced by the genome. if referred to as the complete proteome, it means the proteins produced by a certain cell under specific conditions.

Question 5

Describe the structure of RNA.

Answer 5

It is a polymer made up of repeating mononucleotide sub-units making up a singe strand. each nucleotide is made up of:

• the pentose sugar ribose
• an organic base (A,G,C, or U)
• A phosphate group

Question 6

Which types of RNA are involved in protein synthesis?

Answer 6

• messenger RNA

- transfer RNA

Question 7

Describe the structure of mRNA.

Answer 7

• A long strand
• arranged into a single helix
• has a sequence of bases determined by that of DNA during transcription

Question 8

Describe how mRNA performs its role.

Answer 8

• Once formed, it leaves the nucleus through pores and enters the cytoplasm where it associates with ribosomes
• there it acts as a template for protein synthesis

Question 9

How is the structure of mRNA suited to its function?

Answer 9

It possesses information in the form of codons. these determine the amino acid sequence of a polypeptide.

Question 10

Describe the structure of tRNA.

Answer 10

• single-stranded chain
• folded into a clover shape, with one end extending further than the other, where the amino acid can easily attach
• there are many different types that bind to specific amino acids
• At the opposite end there is a sequence of three other organic bases called the anticodon
• given that the genetic code is degenerate, there must be as many tRNA molecules as coding triplets

Question 11

Describe complimentary base pairing in RNA.

Answer 11

• RNA can join with both DNA and RNA, the complimentary bases are:
  G and C
  A with U (in RNA) or T (in DNA)

Question 12

Describe complimentary base pairing during protein synthesis.

Answer 12

• an anti-codon pairs with three complimentary bases that make up the codon on mRNA