1. Lesson Four
Structure of a Gene

2. Gene Structure What is a gene?
Gene: a unit of DNA on a chromosome that codes for a protein(s)
Exons
Introns
Promoter sequences
Terminator sequences
Other regulatory sequences (enhancers, silencers), which may be far from major components of a gene

3. Gene Structure
Exons: contain the bases that are utilized in coding for the protein
Introns: contain bases that are not utilized in coding for proteins and intervene between the exons
Introns are spliced out

4. Gene Structure
Promoter: bases that provide a signal to tell the cell’s machinery where to begin transcription, usually before or within a gene
Terminator: bases that provide a signal to tell the cell’s machinery where to stop transcription, usually at the end of a gene

5. Gene Structure This gene has 3 exons and 2 introns
A typical gene might look something like this:
This gene has 3 exons and 2 introns
= exon
= promoter
= intron
= terminator

6. Lesson Five
Transcription

7. Transcription
The process of using DNA (a gene) as a template to produce messenger RNA (mRNA)
Occurs in the nucleus
Template strand – the strand of DNA that is accessed to make mRNA
Coding strand – the strand of DNA that is NOT accessed to make mRNA. The mRNA that is made from the template strand will be identical to the coding strand (with the exception of U’s for T’s)

9. RNA Modification Trimming: removing bases from the 5’ and 3’ ends
Capping: adding a methylated G to the 5’ end
Necessary for RNA localization to the ribosome
Tailing: addition of A’s to the 3’ end of the mRNA
More A’s = more stabile mRNA
Splicing: removing introns prior to mRNA transport to the nucleus

11. Lesson Six
Translation

12. Translation
The process of using mRNA as a template to generate a polypeptide that will eventually become a mature protein
Also called protein synthesis
Requires the ‘genetic code’
Based on 64 codons, each with 3 nucleotides
Provides the link between DNA and protein sequence

13. Translation Requires Different Types of DNA
mRNA: messenger RNA; major product of transcription
Represents the code for the primary amino acid sequence of a protein
Only type of RNA that is translated
tRNA: transfer RNA
Recognizes the mRNA code (tri-nucleotide) and brings with it (or transfers) the appropriate amino acid to the protein
Link between mRNA and protein
rRNA: ribosomal RNA
Part of the ribosomes
Involved with translation by helping to align the mRNAs and tRNAs

20. Protein Processing
Final transport

21. Genomics to Proteomics
Primary control of gene expression

22. Lesson Seven
Mutations

23. Point Mutations Involves a single base pair
Substitution, insertion, deletion
SNPs
May not affect amino acid sequence
Same sense (silent, neutral, synonymous, same sense)
Due to redundancy of the genetic code
May affect amino acid sequence (nonsynonymous)
Missense (results from a change in an amino acid)
Nonsense (results from a change to a stop codon – truncated protein)
Frame shift mutations (insertion or deletion of 1+ bases - alters the reading frame)

24. Missense Mutation
Sickle Cell Anemia