RNA Structure and Function Quiz

RNA Structure and Function

• RNA contains ribose sugar, adenine, uracil, cytosine, and guanine bases.
• RNA is single-stranded, but can fold back on itself for base pairing.
• RNA acts as a helper to DNA, enabling protein synthesis.

Types of RNA

• Messenger RNA (mRNA): Carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm for protein synthesis.
• Transfer RNA (tRNA): Transfers amino acids from the cytoplasm to ribosomes for protein synthesis, with each amino acid having a specific tRNA molecule.
• Ribosomal RNA (rRNA): Combines with proteins to form ribosome subunits (large and small), which are essential for protein synthesis.

Ribosomes and Protein Synthesis

• Ribosomes are the sites of protein synthesis.
• They can be free-floating in cytoplasm or clustered as polyribosomes.
• Ribosomes attached to the endoplasmic reticulum (ER) synthesize proteins for the ER.
• Free ribosomes or polyribosomes synthesize proteins for the cytoplasm.

The Genetic Code

• The genetic code uses a triplet code (codon) of three bases to code for a single amino acid.
• There are 61 codons that correspond to specific amino acids, and 3 stop codons signal the end of protein synthesis.
• Methionine's codon is also the start codon, initiating translation.
• Most amino acids have multiple codons, providing some protection against mutations.

Transcription

• Transcription is the process of creating RNA from a DNA template.
• RNA polymerase is an enzyme that binds to a promoter sequence on DNA, opening up the helix.
• RNA polymerase adds complementary RNA nucleotides to the template DNA strand, creating an mRNA molecule.
• The resulting mRNA transcript is a complementary copy of the DNA sequence.

mRNA Processing

• Newly synthesized primary mRNA undergoes processing to become mature mRNA.
• Processing involves:
  • Capping: Adding a modified guanine nucleotide to the 5' end.
  • Poly-A tail addition: Series of adenine nucleotides added to the 3' end.
  • Splicing: Introns (non-coding regions) are removed, and exons (coding regions) are joined together.
• These modifications provide stability and ensure proper functionality of the mRNA molecule.

Translation

• Translation is the process of synthesizing proteins from mRNA instructions.
• It requires mRNA, tRNA, rRNA, and enzymes.
• tRNA: Carries amino acids to ribosomes, with each tRNA molecule recognizing a specific mRNA codon through its anticodon.
• The order of codons in mRNA determines the order in which tRNA molecules bind to ribosomes, dictating the sequence of amino acids in the protein.
• At the ribosome, amino acids are joined together to form a polypeptide chain.