Exam #3: #3 Gene Transcription and RNA Modification

Gene

A segment of DNA used to make a functional product either an RNA or a polypeptide

• Carries out a function

Transcription

First step of gene expression

• Process of making a copy

• Copying of a DNA sequence into a RNA sequence

• Structure of DNA is NOT altered in this process

  • Can continue to store information

Proteins

• DNA base sequences: define the beginning and end of a gene and regulate the level of RNA synthesis

• Proteins must recognize and act on DNA for transcription to occur

Regulatory Sequences

Site for the binding of regulatory proteins

• Regulatory proteins: influence the rate of transcription

*Regulatory sequences: can be found in a variety of locations

Promoter

Site for RNA polymerase binding

• Signals the beginning of transcription

Terminator

Signals the end of transcription

Ribosome-binding Site

Site for ribosome binding to mRNA in bacteria:

• Translation begins near this site in mRNA

In Eukaryotes:

• The ribosome binds to a 7-methylguanosine cap in the mRNA

• Ribosome scans the RNA for a start codon

Codons

3 nucleotide sequences (AUG = Met) within the mRNA that specify particular amino acids (Ex: Ser, Arg, Lys, Leu) 

• Sequence of codons in mRNA determines sequence of amino acids in a polypeptide