Question

Define replication, transcription, and translation.

Short answer

Replication copies DNA, transcription synthesizes mRNA from DNA, and translation produces proteins from mRNA.

Step-by-step solution

Define Replication

Replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. This process is essential for cell division, as it ensures that each daughter cell receives an exact copy of the DNA.

Define Transcription

Transcription is the process by which a segment of DNA is used as a template to generate a complementary RNA strand. This RNA strand is known as messenger RNA (mRNA). It carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis will occur.

Define Translation

Translation is the process by which the sequence of codons on messenger RNA (mRNA) is read by a ribosome to synthesize a specific protein. During translation, transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, where they are joined together in the order specified by the mRNA sequence to form a polypeptide chain.

Key concepts

DNA Replication

DNA replication is a fundamental process that ensures the transmission of genetic information from one generation to the next. It occurs in the nucleus of eukaryotic cells and involves creating two identical copies of a DNA molecule from the original double-stranded DNA.

Key steps in **DNA replication** include:

• **Unwinding the DNA helix**: An enzyme called helicase unwinds the double-stranded DNA
• **Formation of the replication fork**: Single-strand binding proteins stabilize the unwound DNA
• **Synthesis of a new strand**: DNA polymerase adds complementary nucleotides to the template strand
• **Proofreading**: DNA polymerase checks and corrects errors in the newly synthesized DNA strand

DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand. This process is crucial for cell division, ensuring that each daughter cell receives an exact copy of the parent cell's DNA.

RNA Transcription

Transcription is the first step in gene expression, where a specific segment of DNA is copied into RNA, particularly messenger RNA (mRNA). This process takes place in the nucleus in eukaryotic cells.

Core steps in **RNA transcription** include:

• **Initiation**: RNA polymerase binds to a specific region of the DNA called the promoter
• **Elongation**: RNA polymerase moves along the DNA template, synthesizing an RNA strand by adding nucleotides in a sequence complementary to the DNA template
• **Termination**: When the RNA polymerase reaches a terminator sequence, transcription stops and the RNA molecule is released

The mRNA serves as a temporary copy of the gene, carrying the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where it directs the synthesis of proteins during translation.

Protein Translation

Translation is the process by which the genetic code carried by mRNA is decoded to produce a specific protein. This step occurs in the cytoplasm of the cell at the ribosome.

Essential steps in **protein translation** include:

• **Initiation**: The ribosome assembles around the mRNA and the first tRNA, starting at the start codon (AUG)
• **Elongation**: The ribosome travels along the mRNA, reading codons and matching them with the corresponding amino acids brought by tRNA molecules. These amino acids are linked together to form a growing polypeptide chain
• **Termination**: When the ribosome reaches a stop codon on the mRNA, the translation process ends, and the newly synthesized polypeptide chain is released

The polypeptide chain then folds into a functional protein that can perform various activities within the cell. Translation is a critical phase in converting genetic information into functional proteins, which carry out numerous cellular processes.