14.4 Eukaryotic Pre-mRNA Transcripts are Processed prior to Translation.

What is the *difference in gene structure* in Eukaryotes vs. Prokaryotes?

-*Prokaryotes* - DNA sequence is read in the same order as the amino acid sequence. -*Eukaryotes* - Non-coding introns within coding sequence.

What is the *difference in translation and transcription* occurrences in Eukaryotes vs. Prokaryotes?

-*Prokaryotes* - Happens at the same time in the cytoplasm. -*Eukaryotes* - Transcription takes place in the nucleus, then translation in the cytoplasm.

What is the *difference in modification of mRNA after initial transcription but before translation* in Eukaryotes vs. Prokaryotes?

-*Prokaryotes* - Usually none. -*Eukaryotes* -Introns spliced out, 5' end cap and 3' poly A tail added.

What are the mRNA processing steps in eukaryotes?

-Addition of a 5' cap to the beginning of the RNA. -Addition of a poly-A tail (tail of A nucleotides) to the end of the RNA. -Chopping out of introns, or "junk" sequences, and pasting together of the remaining, good sequences (exons).

What is an intron?

A portion of gene within coding region that is transcribed into pre-mRNA, but is spliced out before translation.

What is pre-mRNA?

Initial gene transcript before its modified to make functional mRNA.

What is RNA splicing?

Last stage of mRNA processing in eukaryotes where transcripts or introns are excised through action of small nuclear ribonucleoprotien particles (snRNP). -Splices exons together.

What is the 5' cap?

Methylated guanine nucleotide bound to the 5' end of eukaryotic mRNA. -Aids in transfer out of nucleus through nuclear pore.

What is RNA processing?

Modification of RNA primary transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends.

What is an exon?

Portion of a DNA molecule in eukaryotes that code for polypeptides.