What are Homologous Chromosomes?

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Homologus chromosomes

Homologous Chromosomes are similar in shape and content, and are separated during Meiosis. In an organism that is produced by sexual reproduction, each parent contribues a set of chromosomes grouped into homologous pairs. Homologous chromosomes are chromosomal pairs of the same length, Centromere (region of DNA found near the middle of a chromosome) position and staining pattern, with genes for the same characteristic at corresponding loci (specific location of a gene or DNA sequence on a chromosome). One homologous chromosome is inherited from the organism’s mother, and the other from the organism’s father. They synapse during meiosis, or cell division that occurs as a part of the creation of Gametes. Synapsis is essentially the pairing of 2 homologous chromosomes during meiosis. Homologus chromosomes are only found in “diploid”. For example, Humans are diploid.


What is Ploidy?

Ploidy is the number of sets of chromosomes in a biological cell. Non-homologous chromosomes representing all the biological features of an organism form a set, and the number of sets in a cell is called Ploidy. In diploid (have 2 homologous copies of each chromosome) organisms (most plants and animals), each member of a pair of homologous chromosomes in inherited from a different parent. But polyploidy organisms have more than 2 homologous chromosomes. 


What is Meiosis?

Meiosis is a special form of cellular division that produces daughter (2 cells that are produced when a single cell divides) cells with half the number of chromosomes as the original parent cells. During the first part of meiosis, the homologous chromosomes line up and are separated. Meiosis only occurs in special cells called “germ cells”, and frequently used to produce gametes like egg and sperm. Gametes are sex cells produced during meiosis. Gametes have half the number of chromosomes that are found in a complete organism. Most of the cellular divisions in an organism involve “mitosis” (division of cells to form new You do not have access to view this node). Only those cells involved in reproduction divide by meiosis. In flowering plant, the only place meiotic division takes place is in the “anthers and carpels”. The anther is the part of a flower that produces pollen (sperm particles of plant), which in turn produces the plant’s sperm. The carpel is the female reproductive part of a flower.


How do the Homologous Chromosomes work in humans?

Humans have exactly 46 chromosomes in which 22 pairs are homologous non-sex chromosomes (autosomes), and one pair is sex chromosomes. Half of those were in the egg of the mother and the other half were carried to the egg by the sperm donated by the father. Each of the 23 donated by one parent correspond in shape and content to a chromosome in the set donated by the other parent. These homologous chromosomes pair up to produce a unique human being. Homologous chromosomes work in such a way that Chromosome #1 from one of the parent (father) will have the same number of genes on it as Chromosome #1 from the other parent (mother). Homologous chromosomes are similar in length, except for the sex chromosomes in some groups of one or more organisms, where the X-chromosome (one of the two sex determining chromosome) is considerably larger than the Y-chromosome.  


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