Lecture 11 - Molecular Biology (I) Flashcards
Describe replication.
DNA is replicated to form two double helixes.
Describe transcription.
RNA synthesis, transfer of information from DNA –> RNA
Describe translation.
protein synthesis mRNA sequence is converted to an amino acid sequence via the genetic code
Describe the structure of DNA.
- double helix; two strands of DNA held together by H bonding between the bases
- composition: nucleotides, deoxyribose sugar, phosphate group, base
- one end has a phosphate attached to the 5’ carbon
- one end has a hydroxyl group attached to the 3’ carbon
Where is DNA found in the cell?
nucleus
What are the characteristics of a virus?
a genetic element that replicated within cells but, has extracellular state
- single or double stranded
- DNA or RNA
- linear or circular chromosomes
- often cause disease
What are the characteristics of plasmids?
- found primarily in prokaryotes
- most are double stranded DNA, circular
- unlike viruses, plasmids have no extracellular form and typically do not cause damage to the entire cell
- Plasmids often carry beneficial genes
e. g. antibiotic resistance
List plasmid and virus similarities.
- genetic material replicated within cells
- double stranded DNA, circular
List plasmid and virus differences.
- viruses have an extracellular state
- viruses - can be single or double stranded
- viruses - can involve DNA or RNA
- viruses - often cause disease
- plasmids - often carry beneficial genes
e. g. antibiotic resistance
Describe the effect of heat on DNA.
A higher temperatures, double stranded DNA breaks
–> DNA denaturation (melting)
hydrogen bonds between the two strands break
A lower temperatures, double stranded DNA reforms –> annealing
melting temperature (Tm)
the midpoint temperature for complete denaturation
Tm is proportional to the GC content of the DNA molecule.
As the GC content increases the melting temperature will increase because, it takes more energy to break H bonds between G and C.
Why is replication considered semiconservative?
- One parent DNA ends up in the daughter cell.
- The other is replicated from the parental DNA strand, it is complementary to that parent strand.
Why does replication occur in only one direction?
proceeds from 5’ to 3’ end
- a nucleotide is added to the hydroxyl on the 3’ carbon at the end of the chain
- More precisely, the phosphate on the 5’ carbon of the incoming nucleotide is attached to the hydroxyl chain on the 3’ carbon of the previously added nucleotide chain.
Describe replication at the fork.
i) leading strand, DNA is synthesized continuously
ii) lagging strand DNA is made discontinuously
At lagging strand, RNA primers are synthesized multiple times and DNA pieces are joined up later
Describe transcription.
Key enzyme for transcription os RNA polymerase.
Synthesizes RNA in the 5’ to the 3’ direction
Uses DNA as a template
RNA polymerase does not require a primer
