the cell cycle Flashcards
What are the key chemical components of DNA?
Pentose sugar, phosphate group, and nitrogenous base.
What bonds hold DNA molecules together?
Hydrogen bonds between base pairs and phosphodiester bonds in the sugar-phosphate backbone.
What is the geometry of the DNA molecule?
Double helix with major and minor grooves, 2 nm in diameter, 3.4 nm per helical turn.
What base pairs form in DNA, and how do they bind?
Adenine pairs with Thymine (A-T) and Guanine pairs with Cytosine (G-C) through hydrogen bonds.
What are the key enzymes involved in DNA replication?
h, primase, DNA polymerase, single-stranded binding proteins (SSB), topoisomerase, and ligase.
What are Okazaki fragments?
Short DNA segments synthesized on the lagging strand during replication.
How does eukaryotic DNA replication differ from prokaryotic?
Eukaryotic replication has multiple origins, occurs in the nucleus, involves distinct S phases, and has slower replication with telomere replication.
What is the role of DNA polymerase?
Adds nucleotides to the RNA primer, catalyzes phosphodiester bonds, and proofreads for errors.
What are the main phases of the cell cycle?
G1 (growth and preparation), S (DNA synthesis), G2 (preparation for mitosis), M (mitosis and cytokinesis).
What are cell cycle checkpoints?
Control points where the cell assesses conditions (e.g., DNA damage) before progressing to the next phase.
Why is the G1 phase critical?
It prepares cells for replication and is the phase where cells can exit the cycle into a resting state.
What is the restriction point in the cell cycle?
A checkpoint in G1 where the cell commits to division.
What is the main difference between mitosis and meiosis?
Mitosis produces two genetically identical diploid cells, while meiosis produces four genetically distinct haploid cells.
What events in meiosis create genetic diversity?
Crossing over during Prophase I and independent assortment during Metaphase I.
How does cytokinesis differ in mitosis and meiosis?
Mitosis results in two cells, while meiosis involves two rounds, ultimately producing four cells.
How does the prokaryotic cell cycle differ from the eukaryotic?
Prokaryotes have continuous DNA replication with a single origin, while eukaryotes have defined phases and multiple origins.
What is the significance of the C period in E. coli?
It corresponds to DNA replication and is nearly constant, taking about 40 minutes.
How can E. coli divide with partially replicated genomes?
New replication cycles start before the previous division is complete.
What proteins regulate the cell cycle?
Cyclins and cyclin-dependent kinases (Cdks).
How does the cell respond to DNA damage?
Checkpoints arrest the cycle to allow repair or trigger apoptosis.
What factors determine the timing of cell cycle stages?
Accumulation of regulatory proteins and feedback mechanisms about cellular conditions.
What is flow cytometry used for?
Analyzing cell cycle progression by measuring DNA content and cell size.
What is the significance of the S phase in cell cycle studies?
It represents DNA synthesis, a crucial marker for cell proliferation.
What happens during metaphase?
Chromosomes align at the metaphase plate, and spindle fibers attach to centromeres.
What marks the transition from metaphase to anaphase?
Separation of sister chromatids moving to opposite poles.
What are the key events in telophase?
Chromosomes decondense, and the nuclear envelope re-forms.
What occurs during Prophase I of meiosis?
Homologous chromosomes pair and exchange genetic material (crossing over).
How does Meiosis II differ from Meiosis I?
Meiosis II separates sister chromatids without further DNA replication, producing four haploid cells.
Why is meiosis important?
It ensures genetic variation and produces gametes for sexual reproduction.
