Chapter 15 DNA Transcription/Translation

Describe the two major processes of gene expression.

Transcription (in the nucleus) and Translation (in the cytoplasm).

What is the main function of RNA polymerase?

To read the DNA template strand and build a complementary strand of messenger RNA (mRNA).

What are the functions of mRNA, tRNA, and rRNA in translation?

mRNA: The "recipe" that carries the genetic code. tRNA: The "delivery person" that brings the correct amino acid. rRNA: The main component of the ribosome.

What are the key properties of the codons in the Universal Genetic Code?

Read in three-letter chunks; redundant (multiple codons for one amino acid); one start codon (AUG); three stop codons (UAA, UAG, UGA).

What is the function of an anticodon on a tRNA molecule?

To pair with the complementary codon on the mRNA strand, ensuring the correct amino acid is added.

Describe the basic structure of a ribosome and name its macromolecules.

Two subunits (large and small). Made of rRNA (ribosomal RNA) and proteins.

Describe the key steps of the translation process.

1. mRNA binds to ribosome. 2. Start codon (AUG) is recognized. 3. tRNAs bring amino acids, matching codons. 4. Amino acids are linked into a chain. 5. Process continues until a stop codon is reached.

Describe the roles of the A, P, and E sites on a ribosome.

A site (Arrival): Where a new tRNA arrives. P site (Protein chain): Holds the tRNA with the growing chain. E site (Exit): Where the empty tRNA exits.

Name some modifications made to mRNA in eukaryotic cells.

5' Cap; Poly-A Tail; RNA Splicing (removing introns and joining exons).

What is gene regulation, and what is one example?

The process of turning genes on or off. An example is epigenetics, where chemical tags (like methyl groups) are added to DNA, changing gene accessibility without changing the DNA sequence.

In RNA splicing, what is the difference between an exon and an intron?

Exon: Retained and expressed in the final protein. Intron: Cut out and discarded during splicing.

What is the purpose of having multiple codons for the same amino acid (redundancy)?

It's a safety feature. A small mutation may not change the amino acid, so the final protein remains functional.