Molecular Genetics - The Central Dogma

Question 1

What is gene expression?

Answer 1

When a gene is used to build a protein

Question 2

What is the central dogma of molecular genetics?

Answer 2

Information encoded in DNA travels in one direction, first to make an RNA molecule, which is then used to build a polypeptide

Question 3

What is the one gene-one-polypeptide hypothesis?

Answer 3

Each gene is unique and codes for the synthesis of a single polypeptide

Question 4

What are the two steps involved in gene expression?

Answer 4

1. Transcription: strand of DNA is copied to produce a complementary strand of DNA (occurs in nucleus)
2. Translation: information coded in RNA molecule is interpreted, linking amino acids to make a polypeptide (occurs in cytosol)

Question 5

Messenger RNA (mRNA)

Answer 5

• Carries DNA instructions to ribosome where the protein will be made according to the instructions
• Largest of the RNA molecules, single stranded
• Each polypeptide has its own gene and each of these genes makes a specific mRNA “message”

Question 6

Transfer RNA (tRNA)

Answer 6

• Delivers amino acids to ribosome so a protein can be built
• Unique “cloverleaf” shape due to base-pairing which creates double-stranded regions
• Each amino acid has one or more tRNA molecules which it can bind to
• Since RNA will twist into a helix, the “cloverleaf” 2D shape is actually a T-shaped coiled structure
• Amino acid binds (covalently) to 3’ end of strand

Question 7

Ribosomal RNA (rRNA)

Answer 7

• Important structural component of the ribosome, provides (“scaffolding”) for protein-building process
• Each ribosome contains several rRNA molecules of various sizes
• Some genes code for rRNA, they do not code for a protein