Title: Molecular Genetics: DNA
1Molecular Genetics DNA
- Four roles for DNA
- Information storage
- Replication (reproduction)
- Day to day instructions to the cell
- Mutation
2Molecular Genetics DNA
- Pro- and eukaryotic genes are organized
differently. - Prokaryotic genes are tightly-packed and
streamlined. - Eukaryotic genes are spread out and hard to
control, much more complex.
3The Circular Genome of E. coli
Almost no waste DNA between genes Few repeated
DNA sequences Genes that have to work together
are close to each other Controlled as a unit-
an operon
Genes for lactose metabolism make up an operon
4Eukaryotic genes and genomes
- Generic gene for an mRNA reveals important
features - Interrupted genes (introns and exons)
- Many control regions
- Much wasted DNA
5Example-globin
- Gene families
- Regulation must be coordinated
- Much non-coding sequence between genes
6Example-globin
- Hereditary globin deficiencies are called
thalassemia - Less susceptible to lethal strains of malaria?
- Cooleys anemia
7Molecular Genetics-summary of transcription
- DNA instructions are put into action by RNA,
which is directly copied from a DNA molecule - (transcription)
- Produces different types of RNA
- ribosomal RNA rRNA, messenger RNA mRNA,
transfer RNA tRNA - Some of the RNAs go on to produce protein
- Others have different jobs
8Molecular Genetics-summary of transcription
- Trancription carried out by enzymes called RNA
polymerases - Very large enzymes that are under tight control
by other proteins
9Molecular Genetics-RNA processing
- RNA molecules must be heavily modified after
transcription - This is called RNA processing
10Molecular Genetics-RNA processing
- Eukaryotic mRNA processing most complex
- Involves cutting and splicing of genetic
information
11Molecular Genetics-Roles of RNA
- All RNAs must be processed
- After processing, some of them are directly
active as RNA molecules (rRNA, tRNA, regulatory
RNAs) - One type (mRNA) serves as physical carrier of DNA
information that will be translated into protein
12Molecular Genetics-Roles of RNA
- At least 3 types of RNA required for translation
of proteins - rRNA structure and catalytic heart of ribosome
- tRNA brings amino acids to ribosome-adaptor
- mRNA carries DNA message to ribosome
- Regulatory RNAs are often needed as well
13Molecular Genetics-tRNA
- Adaptor or interpretor-amino acids and mRNA
- Anticodon is complementary to an mRNA codon
- 3 end is covalently attached to an amino acid by
an enzyme
14Molecular Genetics-translation
- Message read one codon at a time
- tRNAs enter and leave successively
- Ribosome forms peptide bonds
15Polyribosome or polysome
16Gene Expression in Prokaryotes
- Expression mainly by controlling transcription
- Constitutive or housekeeping genes expressed
continually-always on - Other genes not produced continually
- Only on when needed
17Operon organization
- Genes that work together are located together
- They are controlled as a unit
- Streamlined, efficient, saves resources
18The genome is organized in units called operons
19Eukaryotic gene expression
- Much more complex
- Many control sequences and proteins for each gene
20Eukaryotic gene expression-transcription factors
- Many proteins must be present for gene to be
active
21Eukaryotic gene expression-transcription factors
- All your somatic cells have the same DNA
- Different tissues have different transcription
factors-different genes are expressed
22Endocrine disruptors
- Environmental pollutants that mimic hormones
- Interact with transcription factors to activate
wrong genes - Birth defects, cancer?