Topic 2: DNA Replication Flashcards
Why is replication essential for organisms?
For cells to divide each daughter cell need to receive a complete copy of the genetic material
Describe common characteristics of polymerases
Can only synthesize DNA in the 5’ to 3’ direction. Can only start adding nucleotides to a primer strand, without it cannot initiate DNA synthesis.
What is the leading strand? What is the lagging strand? How are they same/different?
The leading strand is synthesized continuously, while the lagging strand is synthesized un continuously called Okazaki fragments.
What are primers and why are they needed?
Small sections on the DNA strand, needed to add new nucleotides to the new strand, without it can’t start DNA synthesis.
Clamp loading & sliding clamp proteins
helps DNA polymerase bind and remain associated with the DNA template
Helicase
Unwinds DNA
DNA binding proteins
stabilize unwound DNA strands
Topoisomerases
Breaks and rejoins DNA strands to relieve the tensions on the DNA strand
Primase
Synthesizes primers
Define replisome
complex of enzymes working together during DNA replication (where replication happens)
What does it mean to say that DNA polymerase has “proofreading abilities”?
DNA polymerase can help select correct bases and replace bases that were wrongly incorporated.
How does translesion DNA synthesis help decrease the number of errors that occur during replication?
If proofreading fails, there are specialized DNA polymerases that can replicate across a site of DNA damage (Translesion DNA Synthesis)
What are telomers and why do cells need them? What happens if they are not there?
They are non-coding repeating sequences at the end of the chromosome that shorten with each cell division. Without them can lead to mutations which could lead to cancer development.
How do telomers and telomerase relate to cancer?
Telomerase is an enzyme that can extend telomers. Mutations can lead to cancer development.
Do cells always want to faithfully replicate their DNA?
No do not always want to faithfully replicate their DNA. Helps to add diversity to the gene products we can make. Important for the diversity in the vertebrate and the immune system.
rearrangement
Genes will rearrange during development of beta cells. Each beta cell will have different genes for the variable region.
Somatic hypermutation
Cells is creating mutation in the variable region of the heavy and light chains. Deamination of cytosine creates uracil. Process of fixing this change is error prone leading to mutations that stay in the DNA.
Gene amplification
results from rounds of DNA replication at a specific region of the genome. It increases the number of copies of genes within the cell and therefore the expression of those genes. Can occur normally during development or abnormally in cancer.
