Protein Synthesis

Explain the modifications that occur to mRNA after transcription in eukaryotic cells.

After transcription in eukaryotic cells, mRNA undergoes several modifications to become mature. A 5' cap is added to the beginning of the mRNA, which protects it from degradation and assists in ribosome binding. A poly-A tail is added to the 3' end, stabilizing the mRNA and providing further protection against degradation. Additionally, introns, or non-coding regions, are removed through splicing, leaving only the coding regions (exons) to be exported from the nucleus to the cytoplasm for translation.

Describe the structure of tRNA and its role in translation, including how it pairs with mRNA codons.

tRNA has a cloverleaf structure consisting of three loops and an acceptor stem. Its main role in translation is to carry a specific amino acid to the ribosome, where it helps build the polypeptide chain. The anticodon loop of tRNA pairs with the complementary mRNA codon, ensuring that the correct amino acid is added to the growing chain. This process is crucial for accurately translating the genetic code into functional proteins.

Define transcription and explain the role of RNA polymerase in this process.

Transcription is the process of copying a segment of DNA into RNA. RNA polymerase is the enzyme responsible for reading the DNA template strand and synthesizing a complementary RNA strand. It binds to the promoter region of the DNA, unwinds the DNA strands, and assembles the RNA strand by adding RNA nucleotides that are complementary to the DNA template.

Compare the roles of codons and anticodons in translation. Define each term and explain how they contribute to polypeptide synthesis.

Codons are sequences of three nucleotides on mRNA that correspond to a specific amino acid, while anticodons are sequences of three nucleotides on tRNA that are complementary to the codons on mRNA. During translation, codons on the mRNA are read by the ribosome, and tRNA molecules with the complementary anticodon bring the appropriate amino acid to the ribosome. This process ensures that the amino acids are added in the correct sequence, forming a polypeptide chain.

Proteolysis

Proteasome

What is the function of transcription factors?

Transcription factors are proteins that bind to specific DNA sequences in the promoter region, faciliating the iniation of trascription. These proteins

Ubiquitination

Spliceosome

Name important codons and amino acids (start codons, stop codons, start amino acids)

Start codon: AUG.
Start amino acid: Methionine (Met)

Stop codon: UGA, UAA, UAG

Compare the roles of activator and repressor sequences in gene expression.

Describe the role of transcription factors, promoters, and RNA polymerase in the initiation of transcription.

How do R group interactions contribute to protein structure?

Explain the process of alternative RNA splicing and discuss how it increases protein diversity. Provide an example of a protein produced through this mechanism.