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Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes . [1]
This is an accepted version of this page This is the latest accepted revision, reviewed on 5 January 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis). The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3.
The two chromosomes which pair are referred to as non-sister chromosomes, since they did not arise simply from the replication of a parental chromosome. Recombination between non-sister chromosomes at meiosis is known to be a recombinational repair process that can repair double-strand breaks and other types of double-strand damage. [ 2 ]
During meiosis, 5 of X form one chain, and 5 of Y form another chain. Thus, they behave effectively as a typical XY chromosomal system, except each of X and Y is broken into 5 parts, with the effect at recombinations occur very frequently at 4 particular points. [ 17 ]
Each chromosome consists of two closely associated sister chromatids along their entire length. The chromosomes appear as distinct, well-defined threadlike structures under the microscope. [3] [4] Sex chromosomes, however, are not wholly identical, and only exchange information over a small region of homology called the pseudoautosomal region. [5]
During the leptotene stage, the duplicated chromosomes - each consisting of two sister chromatids - condense from diffuse chromatin into long, thin strands that are more visible within the nucleoplasm (nucleus contents). The chromosomes become visible as thin threadlike structures known as leptonema under a light microscope. [1]: 27 [2]: 353
This is an accepted version of this page This is the latest accepted revision, reviewed on 23 December 2024. DNA molecule containing genetic material of a cell This article is about the DNA molecule. For the genetic algorithm, see Chromosome (genetic algorithm). Chromosome (10 7 - 10 10 bp) DNA Gene (10 3 - 10 6 bp) Function A chromosome and its packaged long strand of DNA unraveled. The DNA's ...