Introduction To Genetics Flashcards
What is molecular genetics?
- Expression and regulation of genes at a molecular level.
- investigative approach that involves the application of laboratory methods and research strategies.
- Sub discipline of genetics. Genes are units of heredity. Molecular genetics is concerned with the physical and chemical properties.
- Understands the nature of inherited characteristics at a molecular level in terms of DNA + RNA structure end sequence and factors that influence gene expression.
- The branch of genetics that deals with hereditary transmission and variation on the molecular level.
Advances in molecular genetics:
- Forensics
- Genetic testing for disease
- Identification of horse meat in British food.
- Ancestral DNA lineage
Flow of Genetic Information
Prokaryotes
DNA - mRNA - Protein
Through transcription and translation.
Flow of Genetic Information
Eukaryotes
DNA
Pre-mRNA
mRNA
Protein
What is transcription?
Copies one of the DNA strands by making a complimentary RNA strand.
5’ to 3’ sequence - based on location of carbon atoms.
Does not require a primer.
What enzyme is involved with transcription?
RNA Polymerases
What does mRNA code for?
Codes for protein and other RNA’s.
What is rRNA?
Part of ribosome
What is tRNA?
Carries amino acids to the ribosome.
What is the level of gene product controlled by?
Transcription regulation
Where does transcription take place?
Eukaryotes
In the nucleus
What happens with transcription in eukaryotes?
After transcription the RNA product travels to its next destination.
mRNA goes to the cytosol where ribosomes translate it.
Where does transcription take place?
Prokaryotes
No nuclear membrane.
mRNA can be translated as soon as made.
What are RNA polymerases?
Enzymes that catalyse the formation of phosphodeister bonds between ribonucleotides.
Form polymers of RNA by copying a DNA template.
Prokaryotic RNA polymerase
What is it made up of?
5 different core subunits and a sigma factor.
β+ and β = 2 large sub units
α = 2 small subunits
ω = 1 small subunit (smallest)
1 sigma factor (various)
Each subunit is a polypeptide chain of amino acids
How is transcription regulated?
Not all genes are expressed all the time.
They can be switch on / off depending on the conditions.
E.g. in response to nutrients, temp or during development. Or to confer specific properties on a cell within a tissue or organ.
What do sigma factors do?
Allow the prokaryotic polymerase to recognise and bind different promoter sequences.
O70 - most prokaryotic promotors
054 - nitrogen-regulates promoters
032 - heat shock regulation promoters
How do species differ with sigma factors?
Have different number of sigma factors.
Typically more sigma factors improves response to changing conditions.
What is the promoter recognition by the bacterial RNA polymerase holoenzyme?
Core RNA polymerase associates with a sigma factor that binds to a specific promoter sequence (green) in the DNA.
Contacting sequences centered at -10 and -35 region.
The α terminal domains contact the up element (orange), which is located upstream of the -35 region on some promoters.
The tighter the bind to the sequence in transcription equals
The higher level of transcription
Key features of prokaryotic transcription
- only 1 RNA polymerase
- sigma factor
- transcription and translation are coupled
- genes contain NO introns
- transcripts can be polycistronic
Key features of eukaryotic transcription?
- 3 RNA polymerases Pol I, Pol II, Pol III
- No sigma factor
- Transcription and translation are NOT coupled
- Genes frequently contain introns
- Transcripts are monocistronic
Steps of transcription
1) initiation
2) elongation
3) termination
Transcription
1) initiation
The most important and complex
