13-Gene Expression

What is name for a segment of DNA that codes for an RNA molecule?

a gene

What to processes have to occur in order for a protein to be produced?

Transcription and Translation

In a bacterial cell, do transcription and translation occur in the same area?

Yes

In a bacterial cell, can a ribosome start to translate and mRNA molecule that has not been finished being made in transcription?

Yes

In a eukaryotic cell, do transcription and translation occur in the same area?

No. Transcription occurs in the nucleus and translation occurs in the cytoplasm.

In a eukaryotic cell, can a ribosome start to translate and mRNA molecule that has not been finished being made in transcription?

No. Because transcription and translation do not occur in the same area.

In gene expression in a eukaryotic cell, what two processes occur between transcription and translation?

RNA processing and export of the RNA out of the nucleus

What is the template in transcription?

A strand of DNA. We will call it the DNA template strand.

What determines which strand of DNA is used as the template for a gene?

The promoter.

What enzyme synthesizes the RNA molecule in transcription?

RNA polymerase

What is the product of transcription?

RNA

What nucleotides are used as monomers during transcription?

ATP, UTP, GTP, CTP

In transcription, if the sequence of the DNA template strand is:

3'-ATGCGATC-5'

What would be the sequence of the RNA?

5'-UACGCUAG-3'

What segment of DNA signals the beginning of transcription?

The promoter

What segment of DNA signals the end of transcription?

The terminator

What occurs in the initiation stage of transcription?

RNA Polymerase binds to the promoter, the DNA strands separate, RNA polymerase initiates synthesis.

What occurs in the elongation stage of transcription?

RNA polymerase reads the DNA template strand from the 3' to 5' end and synthesizes the RNA molecule in the 5' to 3' direction.

What occurs in the termination stage of transcription?

RNA polymerase releases the RNA molecule and detaches from the DNA. In bacteria, this occurs once RNA polymerase transcribes through the terminator.

In a typical eukaryotic gene the coding segments of DNA are interrupted by noncoding regions. What are the coding segments called?

Exons

In a typical eukaryotic gene the coding segments of DNA are interrupted by noncoding regions.What are the noncoding segments called?

Introns

In eukaryotic cells, what 3 things occur in mRNA processing?

1. Addition of a 5' cap to the 5' end

2. Addition of a Poly-A tail to the 3' end

3. Splicing

What is the 5' cap?

A modified guanine nucleotide added to the 5' end.

What is the Poly-A tail?

A string of adenine nucleotides added to the 3' end.

What occurs in splicing?

In splicing, the introns are removed and the exons are attached to each other?

What structure performs splicing?

A Spliceosome

What is alternative splicing?

Alternative splicing is splicing the pre-mRNA in different ways. You always remove the introns and in some cases some of the exons are also left out.

In eukaryotic cells, what process allows a single gene to code for multiple proteins?

Alternative Splicing

What is the template in translation?

mRNA

What is the product of translation?

Protein

What enzyme synthesizes the protein in translation?

Ribosome

What part of the mRNA signals the beginning of translation?

The start codon

What part of the mRNA signals the end of translation?

The stop codon

What is codon?

A codon is a 3 nucleotide long sequence found in mRNA that codes for an amino acid or stop.

What sets the reading frame in translation?

The start codon

What type of RNA has an amino acid attached to it?

tRNA

What type of RNA has an anticodon?

tRNA

What type of RNA has codons?

mRNA

What is an anticodon?

An anticodon is a 3 nucleotide long sequence found in tRNA that is complimentary to one of the codons.

What enzymes connect the correct amino acid to the correct tRNA?

Aminoacyl-tRNA synthetase

What are the names for the 3 sites on the ribosome that are used by tRNA?

1. The aminoacyl site

2. The peptidyl site

3. The exit site

What site on the ribosome binds the tRNA molecule carrying the next amino acid to be added to the protein?

The Aminoacyl site

What site on the ribosome binds the tRNA molecule carrying the growing protein?

The Peptidyl site

Through what site on the ribosome do empty tRNAs leave?

The Exit site

What occurs in the initiation stage of translation?

The mRNA, initiator tRNA, and the two subunits come together to form a complex. At the end of this stage the initiator tRNA will be in the P site of the ribosome.

What occurs in the elongation stage of translation?

The ribosome reads the mRNA in the 5' to 3' direction and synthesizes the protein from the N-terminus to the C-terminus.

In the elongation stage, what determines the specific tRNA molecule that will bind to the A site?

The codon that sits in A site will determine which tRNA molecule will bind.

What occurs in the termination stage of translation?

The ribosome reaches the stop codon. A protein called release factor binds the A site. This causes the protein to be released and the two subunits of the ribosome to separate and release the mRNA.

In eukaryotic cells, what is one function of the 5' cap and Poly-A tail?

They help ribosomes bind to the mRNA molecule.

What is a polyribosome?

It is an mRNA molecule with multiple Ribosomes bound to it.

What is polycistronic mRNA?

It is an mRNA that carries the coding sequences for more than one gene.

In what type of organism would you find polycistronic mRNA?

Prokaryotic