Transcription and Translation

Flashcards about Transcription and Translation based on lecture notes. Includes key processes, enzymes, and steps involved in gene expression.

What is transcription?

The process by which DNA is converted into mRNA (messenger RNA).

What is translation?

The process of converting the information stored in mRNA and using it to build a protein.

Which organelle is used to make proteins?

Ribosome

What are the three steps of Transcription?

Initiation, Elongation, and Termination

What happens during the initiation step of transcription?

RNA polymerase binds to the promoter region of DNA.

What is the promoter region?

A short sequence of DNA (in eukaryotic DNA, often the TATA box: TATA double A).

Where is the promoter sequence located?

25 nucleotides upstream of the site where transcription begins.

In what direction does RNA polymerase synthesize mRNA?

RNA polymerase synthesizes mRNA starting from the 5' end going to the 3' end.

In what direction does RNA polymerase read the DNA strand?

RNA polymerase reads the DNA strand in the 3' to 5' direction.

What is the strand of DNA used to synthesize mRNA called?

Template strand (aka antisense strand)

What is the strand of DNA that is not used to synthesize mRNA called?

Non-template strand (aka sense strand or coding strand)

What happens during the termination step of transcription?

RNA polymerase molecule and mRNA strand separate from the DNA template strand; poly-A tail is added to the 3' end of the mRNA strand.

What is poly-A polymerase?

Enzyme that adds a poly-A tail to the 3' end of the mRNA strand during termination.

Why are both the 5' and 3' ends capped during transcription?

To protect the mRNA strand from being degraded by enzymes.

What are introns?

Longer sequences of nucleotides that do not code for anything and must be removed.

What are exons?

Shorter sequences of nucleotides that are used to synthesize proteins and remain after splicing.

What is the process of removing introns called?

RNA splicing

What happens to the mRNA strand after it is synthesized in the nucleus?

mRNA leaves the nucleus and enters the cytosol, interacts with a ribosome and tRNA to build a protein

What is a codon?

A set of three nucleotides on the mRNA strand that matches with an anticodon on tRNA and codes for a specific amino acid.

What is an anticodon?

A set of three nucleotides on the tRNA molecule that matches with a codon on mRNA.

What are the three steps of translation?

Initiation, Elongation, and Termination

What are the three active sites of a ribosome?

E site, P site, and A site

What is the start codon?

AUG, which corresponds to the anticodon UAC and carries the methionine amino acid.

What is the P site of the ribosome?

Peptidyl site; where peptide bonds are formed.

How do tRNA molecules move through the ribosome during elongation?

tRNA molecules enter the A site and exit from the E site, adding amino acids to the growing polypeptide chain.

What is a polypeptide chain?

Growing chain of amino acids creating a protein.

What are the three stop codons?

UAA, UAG, and UGA.

What happens when a stop codon is read at the A site during translation?

They cause a release factor to enter the A site, disassembling the ribosomal subunits and releasing the protein.

Where does the protein go after translation?

The protein leaves the ribosome and goes to the Golgi body for further processing and modification, including folding into a specific shape.