Introduction to Molecular Biology 2 Lecture Flashcards
29/10/24
Describe the method of semi-conservative replication
DNA helicase breaks the hydrogen bonds between complementary base pairs
Both strands act as a template, and free nucleotides will join to their complementary base pairs.
DNA polymerase rejoins the sugar-phosphate backbone by creating phosphodiester bands.
2 DNA molecules are produced, each containing 1 new strand and 1 old strand.
How long does it take to replicate the human genome?
8 hours
How does replication of the human genome achieve speed?
The genome has multiple origins of replication
In what direction is the growing strand during DNA replication synthesised?
In the 5’ to 3’ direction
There are 2 strands during DNA replication, the growing and the lagging. Describe the nature of these strands
The leading strand is continuously synthesised in a 5’ to 3’ direction
The lagging strand is the opposing strand, which cannot be continuously synthesised because it goes 3’ to 5’. So it is synthesised in fragments (Okazaki fragments). Primers are extended in shorter fragments until the strand is finished. Then the RNA primers are erased and replaced by DNA, altogether sealed by DNA ligase.
What is Werner’s syndrome?
Premature chromosomal ageing, where there is a defect in telomeric replication, caused by a mutation in the WRN gene, so the telomere’s shorten faster than normal.
What is the function of telomerase?
To protect the telomeres (i.e. by extending them)
How can polymerase be responsible for any issues during protein synthesis?
Polymerase incorporates the wrong base every 10,000 bases, which can cause mutations.
How can polymerase prevent mutations from occuring?
It has the ability to proofread during replication.
Describe the process of PCR
PCR is a method of amplifying specific fragments of DNA.
Heat is used to separate strands of DNA.
Allowed to cool so primers can hybridise. Free nucleotides are added along with thermostable polymerase to allow annealing of nucleotides. More cycles = more copies/amplification.
What is the use of PCR?
It can be used to test for the presence of infectious agents - blood testing for viral RNA.
Can be used to test for inheritance patterns.
Give other examples of genetic screening
Some technologies also look for changes in the copy number of chromosomes, for example down syndrome is characterised by an extra copy of chromosome 21.
Describe the process of Sanger Sequencing (DNA)
Chain termination method.
Modified dideoxynucleotides (lack an OH at the 3’ end, essential for the next nucleotide to be added) create fragments of DNA that terminate at every possible section. The sorting of these allowed determination of the sequence of bases using gel electrophoresis.
What is the use of DNA sequencing?
It can be used to identify and treat mutations.
