RNA

Question 1

What is messenger RNA (mRNA)

Answer 1

A type of RNA that carries genetic information from the nucleus to the ribosomes for protein synthesis. It is a single helix consisting of thousands of mononucleotides.

Question 2

How does mRNA leave the nucleus

Answer 2

Through the nuclear pores.

Question 3

What is a codon

Answer 3

A sequence of three bases on mRNA that codes for a specific amino acid.

Question 4

What is the genome

Answer 4

The complete set of genes in a cell, including those found in the mitochondria and chloroplasts.

Question 5

Define proteome

Answer 5

The full range of proteins produced by the genome. This is sometimes called the complete proteome, in which case the term proteome refers to the proteins produced by a given type of cell under a certain set of conditions.

Question 6

Describe the key features of the structure of RNA

Answer 6

• RNA is a polymer made up of repeating mononucleotide sub-units.
• It forms a single strand in which each nucleotide is made up of:
  1) The pentose sugar ribose
  2) One of the organic bases adenine, guanine, cytosine and uracil
  3) a phosphate group

Question 7

Which are the two types of RNA that are key in protein synthesis

Answer 7

• Messenger RNA (mRNA)
• Transfer RNA (tRNA)

Question 8

Describe the structure of messenger RNA (mRNA)

Answer 8

• mRNA is a long single helix strand consisting of thousands of mononucleotides
• The base sequence of mRNA is determined by the sequence of bases on a length of DNA in a process called transcription.
• There are many different types of mRNA
• Once formed, the mRNA leaves the nucleus via pores in the nuclear envelope and enters the cytoplasm, where is associates with the ribosomes. Here it acts as a template for protein synthesis.
• Its structure is suited to its function because it possesses information in the form of codons.
• The sequence of codons determines the amino acid sequence of a specific polypeptide that will be made.

Question 9

Describe the structure of transfer RNA (tRNA)

Answer 9

• tRNA is a relatively small molecule that is made up of around 80 nucleotides.
• It is a single stranded chain folded into a clover leaf shape, with one end of the chain extending beyond the other.
• This is the part of the tRNA molecule to which an amino acid can easily attach.
• There are many different types of tRNA, each of which binds to a specific amino acid.
• At the opposite end of the tRNA molecule is a sequence of three other organic bases, known as the anticodon.
• Given that the genetic code is degenerate, there must be as many tRNA molecules as there are coding triplets.
• However, each tRNA is specific to one amino acid and has an anticodon that is specific to that amino acid.

Question 10

List the bases that pair up via complementary base pairing

Answer 10

Cytosine with Guanine
Adenine with uracil (RNA) or thymine in (DNA)

Question 11

Briefly describe/summarise the roles of tRNA and mRNA in protein synthesis

Answer 11

• During protein synthesis an anticodon pairs with the three complementary organic bases that make up the codon on mRNA
• The tRNA structure with its end chain for attaching amino acids and its anticodon for complementary base pairing with the codon of mRNA, is structurally suited to its role of lining up amino acids on the mRNA template during protein synthesis.