Which of the following does not represent a way in which meiosis and mitosis differ?
Similarities between mitosis and meiosis | don’t memorise
Eukaryotic cell division occurs during both mitosis and meiosis. The primary distinction between these divisions is that each method has different objectives. Mitosis is a cell division process that creates two genetically identical daughter cells from a parent cell. When you develop, you go through a process called mitosis. You want all of your new cells to share the same DNA as the ones that came before them. Meiosis is a cell division process that produces sperm or eggs, also known as gametes. The resulting gametes do not have the same genetic makeup as the parent cell. Gametes are haploid cells, meaning they only have half the DNA of their diploid parents. This is done so that when sperm and egg fertilize, the resulting zygote has the correct amount of DNA—not twice as much as the parents. Mitosis is the process by which the zygote divides.
Figure 1: (PageIndex1) This is a tiny embryo that is just starting to develop. If an egg is fertilized, the single cell that results must divide several times in order to grow into a fetus. (Nina Sesina from Wikimedia Commons; CC BY-SA 4.0).
The union of two specialized cells called gametes, each of which contains one set of chromosomes, is required for sexual reproduction. When gametes come together, they form a zygote, which is a fertilized egg with two sets of chromosomes. (Note: Haploid cells have one set of chromosomes; diploid cells have two sets of chromosomes.) If a sexually reproducing species’ reproductive cycle is to continue, the diploid cell must reduce the number of chromosome sets in order to produce haploid gametes; otherwise, the number of chromosome sets will double with each subsequent round of fertilization. As a result, sexual reproduction necessitates nuclear division, which halves the number of chromosome sets.
Diploid animals and plants, as well as certain unicellular species, have two sets of chromosomes. The nucleus of each somatic cell (all cells of a multicellular organism except gametes and reproductive cells) comprises two copies of each chromosome, referred to as homologous chromosomes. Homologous chromosomes are paired chromosomes that have the same genes in the same positions along their length. Each homologous chromosome is inherited in one copy by diploid species from each parent.
Haploid vs diploid cell and cell division
…if there is one event throughout the entire evolutionary sequence at which my own mind still lets my awe overwhelm my instinct to analyze, and where I would admit that Darwinian gradualism does not hold sway over almost all, it is the initiation of meiosis.
— Figure 1 Our theory is depicted as a timeline of events in the history of meiosis in this diagram. Long-term events (evolutionary timescale or multi-generation) are indicated by thick arrows, while the proposed parameiosis mechanism is indicated by a thin arrow. Our theory does not rule out the possibility that meiosis promotes intergenic recombination, resulting in new variation for selection to act on. Indeed, one of us has suggested that the advantages of increased intergenic recombination were significant in eukaryotic cells competing for niches with prokaryotic cells during their early evolution (Holliday 2006). This advantage of meiosis, however, did not provide the initial selective pressure for its roots, as we argue here. Although our hypothesis varies from conventional views on the benefits of meiosis, it is supported by evidence, and its core premise—that recombination must be regulated in order to ensure the fidelity of genetic complement transmission—can be tested. Thank You Notes We appreciate the feedback on an early draft of this article from Francisco Ayala, James F. Crow, and William Holloman, as well as Michael Lynch and two anonymous referees on the original submitted edition. We also thank Richard D’Ari and Arthur Lesk for alerting us to the findings of Ishioka et al. (1998) and Lynch’s study, respectively (2005). Bibliography
Mitosis and meiosis simulation
In response to SARS-CoV-2, scientists and public health organizations around the world worked tirelessly to obtain emergency use authorization and rapid implementation of antibody-based countermeasures, such as therapies and vaccines. Their efficacy is usually calculated in a neutralization assay, but dealing with SARS-CoV-2 is difficult due to biosafety concerns. We look at how pseudovirus can be used as a replacement tool.
In January, the EMBL-EBI announced the launch of the GIFTS (Genome Integrations with Feature and Sequence) platform. This will provide Ensembl and UniProt users access to all of the most recent genomic and protein data for human and mouse genomes. To learn more, Technology Networks talked with the scientists behind GIFTS.