Biology 205-Lecture 11

Transcription and Translation

What does it mean by prokaryotic transcription and translation have no spatial nor temporal separation?

It means prokaryotic transcription and translation occur in the same place and at the same time

Besides the fact that there is no temporal nor spatial separation, why can we couple translation and transcription in prokaryotes?

Because no post transcriptional modification of the mRNA occurs

Where does eukaryotic transcription occur?

In the nucleus

Where does eukaryotic translation occur?

In the ribosomes of the endoplasmic reticulum located in the cytoplasm

Which cells produce mRNA?

Both prokaryotes and eukaryotes

What is the function of mRNA?

Guides the synthesis of proteins

What is functional RNA?

RNA with a unique function that is the final product of transcriptional and is not translated into proteins

What is the function of t-RNA?

Transfers amino acids into the cytosol and builds the polypeptide chain

What is the function of rRNA?

Make up the ribosomes in eukaryotes and prokaryotes

What is the function of snRNA?

Makes up the spliceosomes

Why are snRNA only found in eukaryotes?

Because only eukaryotic cells undergo splicing

What is the function of miRNA?

Modify the amount of gene expression

Which cells contain miRNA?

Eukaryotes

What is the function of the template/anti-sense strand in translation?

Used as a template to make an mRNA strand that’s a copy of the DNA coding strand

What direction does Polymerase II add nucleotides to the growing polypeptide chain?

It elongate sin the 5’-3’ end so it only adds nucleotides to the 3’ end

What is the function of a transcription factor?

Bind where there is a gene for transcription and initiate the binding of RNA polymerase

What is the function of RNA polymerase 1?

Transcribes rRNA genes

What is the function of RNA polymerase II?

Makes mRNA molecules

What is the function of RNA polymerase III?

Makes other functional RNA molecules

Why is splicing in eukaryotes crucial?

Failure to splice or improper splicing interrupts the order of the amino acids in the polypeptide chain

What are the three steps of splicing?

1) Recognize where introns begin and end

2) Grab and hold the intron in the right position

3) Catalyzes the reaction that splices introns

What nucleotides indicate the start and end of an intron?

Gu at the start and AG at the end

How does alternative splicing benefit us?

Because the exons can be rearranged in many different ways, the body can produce a variety of of similar proteins with a slight difference in function

How do introns vary within a gene?

What is considered an intron changes depending on the genes needs