What are DNA Transcription and RNA Translation ?

Transcription is the process in which the information stored in DNA (the cell’s genetic blueprint) is copied into a different molecule called RNA (ribonucleic acid). This RNA molecule then carries the information needed to make a specific protein.

How Does Transcription Work?

1. DNA Unwinds: Inside the nucleus, a section of the DNA “unzips” or unwinds, exposing the sequence of bases (like a ladder splitting down the middle). The DNA in that section has the instructions, or gene, needed to make a specific protein.

2. RNA Building Blocks Line Up: An enzyme called RNA polymerase attaches to the DNA and begins to “read” the sequence of bases on one of the DNA strands. This enzyme builds a strand of messenger RNA (mRNA) by linking together RNA building blocks in a sequence that matches the DNA code.

3. Copying the Code: As the RNA polymerase moves along the DNA strand, it creates a complementary strand of RNA. The sequence of the RNA is like a “mirror image” of the DNA sequence, so it carries the same information but in RNA form.

4. mRNA Detaches: When the entire gene has been transcribed, the newly formed mRNA strand detaches from the DNA. The DNA “zips” back up, returning to its original double-helix structure.

Why is This Important?

• The mRNA molecule now has a copy of the instructions to make a specific protein.

• This mRNA leaves the nucleus and moves into the cytoplasm, where ribosomes (the cell’s protein factories) use the RNA instructions to assemble the protein in a process called translation.

Why RNA Instead of DNA?

DNA stays safely in the nucleus to protect its genetic information. RNA acts as a temporary copy that carries information out of the nucleus, ensuring that the original DNA remains intact.

In short, transcription is the cell’s way of copying DNA instructions into a form that can leave the nucleus and guide protein production, making it essential for all cellular activities and functions.

1. Introducing Ribosomes: The Cell’s Protein Factories

Ribosomes are tiny structures found in both the cytoplasm and attached to some cell membranes, like the rough endoplasmic reticulum (ER). They’re like the cell’s construction sites or factories dedicated to building proteins.

• Structure: Ribosomes are made of two main parts, called subunits (a large subunit and a small subunit). Each subunit is made up of ribosomal RNA (rRNA) and proteins.

• Location: Ribosomes can either float freely in the cytoplasm or be attached to the rough ER. Those in the cytoplasm make proteins that stay inside the cell, while those on the rough ER usually make proteins that will be sent out of the cell or used in the cell membrane.

Ribosomes don’t have “brains,” but they’re extremely efficient at following instructions to assemble proteins from amino acids.

2. How RNA (mRNA) Conveys Instructions to Ribosomes

Once messenger RNA (mRNA) has been created through transcription (as we discussed), it carries the genetic instructions from the DNA to a ribosome in the cytoplasm. Here’s what happens next:

1. mRNA Leaves the Nucleus: After transcription, the mRNA molecule exits the nucleus through tiny openings called nuclear pores and enters the cytoplasm.

2. Ribosome Reads the mRNA Code: The ribosome attaches to the mRNA and begins “reading” the sequence of bases (the A, U, C, and G letters) in sets of three-letter “words” called codons. Each codon codes for a specific amino acid (the building blocks of proteins).

3. Building the Protein: As the ribosome reads each codon, it matches it with the correct transfer RNA (tRNA), which carries the specific amino acid that the codon codes for. The tRNA brings its amino acid to the ribosome, and the ribosome links these amino acids together in the correct sequence, forming a chain.

4. Protein Chain Grows: The ribosome moves along the mRNA, reading codon by codon, and adding amino acids one by one, forming a long protein chain. When it reaches the end of the mRNA, the ribosome releases the completed protein.

3. Why Are Ribosomes Important?

Ribosomes play a critical role in cell function because proteins are essential for nearly every task in the cell, from building structures to carrying out reactions. Ribosomes ensure that each protein is assembled accurately, according to the specific instructions from the DNA.

Without ribosomes, cells would have no way to build the proteins they need to function, repair themselves, grow, and carry out specialized tasks. This makes ribosomes essential for all life.

Summary of the Journey

1. DNA holds the genetic code in the nucleus.

2. Transcription copies a section of DNA into mRNA.

3. mRNA exits the nucleus and delivers the code to a ribosome.

4. The ribosome reads the mRNA and assembles a protein by linking amino acids in the correct sequence.

This process of translating the genetic code into functional proteins is called translation, and it’s how cells turn DNA instructions into the “action” of life.