Introduction to Transcription and Translation

Introduction to Transcription and Translation

• Transcription is the process of copying a segment of DNA into RNA.
• Translation is the process of decoding the RNA sequence into a specific amino acid sequence, forming a polypeptide chain (protein).
• These two processes are fundamental to gene expression, enabling cells to synthesize proteins from the instructions encoded in DNA.
• The processes are highly regulated to ensure appropriate protein synthesis.

Transcription

• DNA serves as the template for mRNA synthesis.
• Specific regions on DNA, including promoters and enhancers, are involved.
• RNA polymerase is the enzyme responsible for synthesizing mRNA.
• The enzyme binds to the promoter region of the DNA, initiating transcription.
• The sequence of bases in the DNA template is copied into a complementary sequence in the mRNA.
• Uracil (U) replaces thymine (T) in mRNA.
• The mRNA molecule is synthesized in the 5' to 3' direction.
• Eukaryotic transcription is more complex than prokaryotic, involving additional steps and regulatory factors.
• mRNA is processed before leaving the nucleus in eukaryotes.
• Introns are removed, and exons are joined together to form a mature mRNA molecule.
• This mature mRNA carries the genetic code from the DNA to the ribosomes in the cytoplasm.

Translation

• Translation occurs in the cytoplasm where ribosomes are located.
• mRNA carries the genetic code from DNA.
• Transfer RNA (tRNA) molecules bring amino acids to the ribosome.
• Each tRNA molecule has an anticodon that is complementary to a specific codon on the mRNA.
• The ribosome reads the mRNA codon sequence.
• Each mRNA codon corresponds to an amino acid.
• tRNAs deliver the appropriate amino acid to the ribosome.
• Peptide bonds form between adjacent amino acids, building the polypeptide chain.
• The polypeptide chain continues to grow until a stop codon is reached on the mRNA.
• A release factor binds to the stop codon, causing the ribosome to release the polypeptide.
• The polypeptide folds into a functional protein.

Genetic Code

• The genetic code is universal, meaning the same codons code for the same amino acids in almost all organisms.
• The genetic code is degenerate; multiple codons can code for the same amino acid.
• There are three stop codons, which signal the end of translation.
• The genetic code is non-overlapping, meaning a base is only read once.

Differences between Prokaryotic and Eukaryotic Transcription and Translation

• Prokaryotic transcription and translation occur simultaneously in the cytoplasm.
• Eukaryotic transcription takes place in the nucleus, while translation occurs in the cytoplasm.
• Eukaryotic mRNA is processed (capping, splicing, polyadenylation) before translation.
• Prokaryotic mRNA is often polycistronic, encoding multiple proteins, while eukaryotic mRNA usually encodes a single protein.

Key Players in Transcription

• RNA Polymerase (initiates synthesis)
• Promoters (regions where transcription begins)
• Enhancers (regulatory regions that promote transcription)
• Transcription Factors (proteins that bind to promoters and enhancers)

Key Players in Translation

• Ribosomes (facilitate polypeptide synthesis)
• Transfer RNA (tRNA) (brings amino acids)
• mRNA (carries genetic code)

This quiz covers the essential processes of transcription and translation in molecular biology. Learn how DNA is transcribed into RNA and how this RNA is then translated into proteins. Understanding these processes is crucial for grasping gene expression and protein synthesis.