Introduction to Molecular Biology 2 Flashcards
In which direction does DNA polymerase flow?
From 5’ to 3’
What directions is the leading and lagging strand?
Leading: 3’-5’
Lagging: 5’-3’
Explain how Okazaki fragments are made on the lagging strand
The clamp that hold the DNA pol for the lagging strand dissociates when finished with an Okazaki fragment. As the helicase unwinds the DNA the DNA primase synthesizes an RNA primer. The DNA pol binds again and is bound to the clamp. DNA pol replicates until it reaches another old RNA primer. The old RNA primer is replaced by DNA and DNA ligase seals the Okazaki fragments
Explain how DNA eeplication occurs at the ends of DNA
A protein telomerase carries an RNA template which allows the synthesis of more template DNA for the template strand. This allows the lagging strand to make a regular Okazaki fragment
How do we protect from DNA mutations?
DNA polymerase has proof reading abilities. It has an E site proof reads and removes errors as the helix winds
There is also post replication proof reading with proof reading exonucleases
Explain the polymerase chain reaction
the DNA double strand is separated by heat. When the two strands are cooled, RNA primer, DNA polymerase and nucleotides are added so the DNA recognizes to replicate the strand to create two double strands form the one double strand.
What is the problem of the ends of chromosomes?
These ends pose a problem for DNA replication. The DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow, gradual shortening of the chromosome.
In the lagging strand, there’s no way to get the fragment started because the primer would fall beyond the chromosome end.
Give an example of how DNA replication can be used in a clinical setting
Use this method to find out if someone has an infection or disease
The number of copies of DNA that are made and how many PCR cycles are done to find a positive infection result can tell how sick a person is.
Explain how DNA sequencing works
DNA Polymerase always acts on the 3’ OH
Adding dideoxyribonucleoside will stop DNA replication
You can add dideoxyribonucleoside for t, a, c, g and it will stop relicating at that base.
This helps us map the DNA by putting where the replication stops onto a map for each base
How is DNA sequencing used in a clinical setting?
Computerized sequencing can see when there are duplications or missing sequences by seeing where each base is and mapping it out with other family members
