WEEK 8 - DNA REPLICATION Flashcards
It can destroy an organism if it occurs in a vital position in the DNA sequence.
MUTATION
- A disease that causes (in Europe and North
America) more than 20% of human deaths each year. - Uncontrolled cell proliferation
CANCER
Very stable under
physiological conditions;
DNA DOUBLE HELIX
What do base pairs require to separate two strands in a test tube?
TEMPERATURE APPROACHING BOILING WATER
What are occasional genetic changes that enhance long-term survival called?
Mutations
Which proteins are needed to open the DNA double helix?
- These proteins are crucial for the unwinding process during DNA replication.
DNA helicases and single-strand DNA-binding proteins
- They hydrolyze ATP when bound to single strands of DNA
- Unwind the DNA double helix.
DNA HELICASE
- They stabilize the unwound, single-strand conformation
- Prevent the DNA from re-annealing.
- Bind tightly to exposed single-strand DNA without covering the bases, which therefore remain available as
templates. - Are unable to open a long DNA helix directly
Single-strand DNA-binding (SSB) proteins
Other term for Single-strand DNA-binding (SSB) proteins
helix-destabilizing proteins
- They prevent DNA tangling
- Relieve over winding of the DNA helix.
DNA Topoisomerases
- Produces a transient single strand break in DNA
- This allows DNA helix sections to rotate freely to relieve tension.
topoisomerase I
- Creates a transient double-strand break in the DNA helix
- This enzyme facilitates the passage of one double helix through another
topoisomerase II
What is the mechanism used by the cell to copy the nucleotide sequence of DNA?
- This process involves separating the DNA helix into two template strands.
DNA templating
What is the term for the localized region of replication that moves along the parental DNA double helix?
- This is where DNA polymerase synthesizes new daughter strands.
Replication fork
In what direction can DNA polymerases synthesize DNA?
5ʹ-to-3ʹ direction
- Pieces of DNA synthesized in the 5ʹ-to-3ʹ direction
- They are joined together after synthesis to create long DNA chains.
Okazaki fragments
- The daughter strand that is synthesized continuously
- This strand is synthesized in the same direction as the replication fork movement.
LEADING STRAND
- The daughter strand that is synthesized discontinuously
- This strand is synthesized through a ‘backstitching’ mechanism.
LAGGING STRAND
What is the first proofreading step in DNA replication performed by?
- This step occurs just before a new nucleotide is added to the growing chain.
DNA polymerase
- Incorrect nucleotides are clipped off at the primer terminus
- This process ensures high fidelity in DNA replication.
exonucleolytic proofreading
