Cell Division: Mitosis and Meiosis Flashcards
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What is the primary purpose of the G2 checkpoint in the cell cycle?
Answer: To ensure DNA replication is complete and accurate before mitosis begins
The G2 checkpoint verifies that DNA has been fully and accurately replicated and that no damage exists before the cell commits to mitosis.
What is nondisjunction, and what is its primary consequence?
Answer: Failure of homologous chromosomes or sister chromatids to separate properly, resulting in aneuploidy
Nondisjunction is the improper separation of chromosomes during cell division, producing daughter cells with abnormal chromosome numbers (aneuploidy), as seen in Down syndrome (trisomy 21).
Which processes during meiosis most directly contribute to genetic variation in offspring?
Answer: Crossing over during prophase I and independent assortment of homologs
Crossing over creates new allele combinations on chromosomes, while independent assortment randomly distributes maternal and paternal chromosomes, generating unique gametes.
Which of the following events characterizes telophase of mitosis?
Answer: Nuclear envelopes reform around each set of chromosomes at the poles
During telophase, nuclear envelopes reform around the chromosomes at each pole and chromosomes begin to decondense, essentially reversing prophase.
What is the key difference between mitosis and meiosis in terms of number of cell divisions and final cell count?
Answer: Mitosis involves one division producing two diploid cells; meiosis involves two divisions producing four haploid cells
Mitosis is a single division producing two genetically identical diploid cells, while meiosis consists of two sequential divisions producing four genetically diverse haploid cells.
In which types of organisms does meiosis occur?
Answer: Only in sexually reproducing eukaryotes
Meiosis is the specialized cell division that produces gametes and occurs only in the gonads of sexually reproducing eukaryotic organisms.
What is the biological significance of the S phase in the cell cycle?
Answer: Each chromosome is duplicated so both daughter cells receive a complete, identical genome
During S phase, the entire genome is replicated so that after cell division, both daughter cells receive a complete and accurate copy of the DNA.