Chapter 10

Introns

intervening regions of the pre-mRNA

Exons

Expressed regions of the pre-mRNA

Splicing

removes introns and connecting exons

3 stages of transcription and translation

Initiation, Elogation, and Termination

Transcription

produces an RNA copy of a gene 

mRNA

a type of RNA that carries information from the DNA to cellular components called ribosomes. 

Translation

process of synthesizing a specific polypeptide

Gene

an organized unit of nucleotide sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the information of  a functional product. 

tRNA 

a molecule with two functional sites; open site, termed the anticodon, binds to a codon in mRNA; the second site, called the 3’ single stranded region, is where an appropriate amino acid is attached. 

Initiation stage in transcription

The promoter functions as a recognition site for sigmas factor. RNA polymerase is bound to sigma factor, which causes it to bind to the promoter. The DNA is unwound to form an open complex. 

Elongation in transcription 

Sigma factor is released, and RNA polymerase slides along the DNA in an open complex to synthesize RNA. 

Termination in transcription

when RNA polymerase reaches the terminator, it and the RNA transcript dissociate from the DNA. 

Initiation in translation

a complex is formed between an mRNA molecule, the first tRNA and the ribosomal subunits 

Elongation in translation

the covalent bonding of amino acids to each other, one at a time, to produce a polypeptide. 

Termination in translation 

when a stop codon is reached in the mRNA

Bacteria

• transcription of DNA to RNA in the CYTOSOL

• Pre-mRNA processing into mRNA - NOOOO

• Translation occurs in the ribosome/ cytosol

Eukaryotes

• Transcription of DNA to RNA in the NUCLEUS

• Pre-mRNA processing into mRNA in the NUCLEUS

• Translation occurs in the ribosome/cytosol