Lesson Four

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
  cells machinery where to begin transcription,
  usually before or within a gene
• Terminator bases that provide a signal to tell
  the cells machinery where to stop transcription,
  usually at the end of a gene

5
Gene Structure

• 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 Us for Ts)

8
(No Transcript)
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 As to the 3 end of the
  mRNA
• More As more stabile mRNA
• Splicing removing introns prior to mRNA
  transport to the nucleus

10
(No Transcript)
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

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
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
25
(No Transcript)