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DNA is replicated in a _______ manner during the S phase of the cell cycle.
DNA replication occurs at _______ where DNA is unwound and replication bubbles form, each containing two replication forks.
Prokaryotes have a ______ origin point, eukaryotes have _____.
The DNA must be _____ prior to being processed for replication. This is controlled by a ____.
The two strands are stabilized such that they do not reassemble due to the attachment of _______.
single stranded binding proteins (SSBP)
In prokaryotes, the majority of DNA is synthesized by _____.
DNA polymerase III
DNA cannot begin synthesis of a DNA strand without the availability of a 3' end of an existing sugar phosphate backbone. This problem is circumvented by first synthesizing an RNA primer to provide an available 3' end for the DNA polymerase to use. The primer is created using ______ and is 5-15 nucleotides long.
primase (an RNA polymerase)
As the bubble enlarges, kinks in the DNA are eliminated by _______.
Due to the antiparallel nature of the DNA, one strand can effectively be synthesized continuously (the______) while the other must be synthesized discontinuously (the _____) in _______.
leading strand, lagging strand, Okazaki fragments
On the 5' end of each Okazaki fragment is an RNA primer which is eventually digested and replaced with DNA by ______that attaches to the 3' end of the upstream Okazaki fragment and extends the DNA replacement.
DNA polymerase I
The DNA of the new strand is eventually joined together by ____.
_______is involved with DNA repair.
DNA polymerase II
Eukaryotes have a different set of DNA polymerases:(3)
- lpha (involved in priming DNA for replication,
- beta and epsilon (involved in DNA repair),
- gamma (synthesizes mitochondrial DNA) and delta (involved in replicating most nuclear DNA)
The RNA primer is not removed by a DNA polymerase in eukaryotes, but instead by a pair of ______.
_____endonuclease recognizes the union of RNA and DNA strands and nicks the backbone at such locations ____ is an RNA exonuclease that then digests the RNA primer which in turn is replaced by DNA polymerase alpha.
HI , FEN1
What is Mitosis?
is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components.
What is Meiosis?
is a special type of cell division necessary for sexual reproduction. In animals, meiosis producesgametes (sperm and egg cells)
What are the phases and their functions for Mitosis?
- Prophase- Nuclear envelope disassociates. DNA condenses and chromosomes become visible, microtubules attach to kinetochores on centromeres and direct their movement to the equatorial plane.
- Metaphase- Centromeres line up along the equatorial plane such that one member of each sister chromatid pair is oriented toward one pole and the other sister chromatid toward the other pole.
- Anaphase- Sister chromatids separate from each other (becoming chromosomes) and migrate to opposite poles directed by microtubules.
- Telophase- Two nuclear envelopes reassemble, DNA decondenses.
What are the phases and their functions for Meisosis?
- Prophase I- Nuclear envelope disassociates, Chromosomes condense, homologous chromosomes pair in synapsis. Synaptomenal complex forms, Chiasmata become visible, crossing over occurs. Chromosomes move due to microtubules.
- Metaphase I- Homologous chromosomes line up on opposite sides of the equatorial plane. The arrangement of each homologous pair is independent of the other nonhomologous pairs.
- Anaphase I- Homologous chromosomes segregate and move to different poles.
- Telophase I- Variable across species
- Prophase II- similar to prophase of mitosis
- Metaphase II- similar to metaphase of mitosis
- Anaphase II- similar to anaphase of mitosis
- Telophase II- similar to telophase of mitosis