A homologous chromosome comes to one the a pair the chromosomes with the same gene sequence, loci, chromosomal length, and centromere location. A homologous pair consists of one paternal and one maternal chromosome. In humans, there space a complete of 46 chromosomes in the nucleus of a somatic cell. Half of them (22 autosomes + X or Y chromosome) are inherited native the father and also the other fifty percent (22 autosomes + X chromosome), native the mother. Each maternal chromosome has actually a corresponding paternal chromosome; lock pair up during meiosis. Typically, a woman will have actually 23 homologous chromosomes vice versa, a male will have 22. The is since the sex chromosomes, X and Y, in males room not homologous. The pairing increase of homologous chromosomes throughout meiosis is important to promote hereditary variation. Since of the hereditary recombination the occurs between homologous pairs at meiosis, the resulting haploid gametes save chromosomes that space genetically various from every other. This amplifies gene pool, thereby, increasing the chances of acquiring genes vital to organic fitness and survival.

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Homologous chromosome definition

In biology, homologous chromosomes room paired chromosomes. They basically have the same gene sequence, loci (gene position), centromere location, and also chromosomal length. Although lock may have actually the same genetic sequence and also loci, they might differ in alleles. The homologous pair is comprised of a paternal chromosome and a maternal chromosome. This chromosomes pair up during meiosis yet not during mitosis.


Etymology

The hatchet homologous came from Greek homologos, an interpretation “agreeing” or “of one mind”. That is a mix of homos, an interpretation “same” and logos, meaning “relation”. The ax chromosome to be coined in 1889 by German anatomist, Wilhelm von Waldeyer-Hartz. It was acquired from the Greek khrōma, definition “color” due to the fact that it conveniently stained with straightforward dyes. Synonym: homologue.

Homologous chromosomes vs. Heterologous chromosomes

When chromosomes space homologous, it way that they room the same, at least in regards to the gene sequences and also loci. Heterologous, in essence, method “different”. This means that heterologous (non-homologous) chromosomes would, therefore, pertain to any two chromosomes that space different, such as in regards to gene sequence and also loci. During meiosis, homologous chromosomes may naturally exchange hereditary material. Heterologous chromosomes perform not. However, there space instances inside heterologous chromosomes perform exchange chromosomal parts. When this occurs, the procedure is called chromosomal translocation. That is a form of mutation that can lead to severe chromosomal aberrations. Because that the comparison between homologous chromosomes and heterologous chromosomes, view table below.

Homologous chromosomes have actually alleles ~ above the very same genes situated in the same loci. Heterologous chromosomes have alleles on different genes.
Pairs up throughout meiosis Does no pair up throughout meiosis
Gene exchanges may occur at synapse. Gene exchanges may occur at translocation.
Basic parts:

centromere (kinetochore) lengthy arms (q) brief arms (p)
Basic parts:

centromere (kinetochore) lengthy arms (q) quick arms (p)
Examples:

22 autosomal chromosomes XX sex chromosomes
Examples:

XY sex chromosome any type of chromosome that supposedly belongs to a chromosomal pair

Homologous chromosome vs. Sister chromatids

At meiosis, each of the homologous chromosomes is made up of two similar chromatids joined together by a usual kinetochore (centromere). The similar chromatids are specifically called sister chromatids to differentiate them from the so-called non-sister chromatids. Prior to cell divisions, the chromosomes in the nucleus show up as threadlike strands (called chromatins). When a cell is fated to experience mitosis or meiosis, lock condense right into thicker structures. By this time, the chromatin is referred to as a chromosome. The DNA in the chromosome replicates through DNA replication during the S phase of the interphase. After ~ replicating, over there would have been 2 DNA copies, each present in a strand dubbed chromatid. The 2 chromatids joined by a common centromere are referred to as sisters chromatids. The chromatids that the various other member of a homologous pair are referred to as non-sister chromatids.


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Homologous chromosomes showing sister and also non-sister chromatids. Genetic recombination deserve to occur between non-sister chromatids.

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Characteristics

The chromosomes of a eukaryotic bio cell are situated in the nucleus. The chromosomes in the nucleus space of two sets. One set would come indigenous the masculine gamete (sperm cell) and the other set, from the mrs gamete (egg cell). Before fertilization, both gametes space haploid. Once the sperm cell successfully fertilizes the egg cabinet the result zygote is a diploid, which method the union of the two haploid cells outcomes in a solitary cell v two set of chromosomes: one set that is maternally-derived and also another collection that is paternally-derived. Every maternal chromosome has a matching paternal chromosome of the very same gene sequence, gene loci, chromosomal length, and centromere location. The pair come close to every other throughout meiosis so the they could exchange genes between sister and non-sister chromatids. Return both members the the homologous pair have similar genes and loci, they might differ in the alleles. Because that example, both of them lug genes coding for the eye shade trait. One has actually alleles for the brown-eye properties whereas the other, because that the blue-eye trait. In this case, the alleles room different and the homologous chromosomes are explained as heterozygous. Top top the contrary, as soon as the alleles room the very same (e.g. Both alleles for the same gene code for the blue-eye trait) then, castle are said to it is in homozygous. The definition of alleles was demonstrated by Gregor Mendel through his pioneering functions in genetics using garden peas. He was able to display that among the alleles might be leading over the other. In this case, only one allele will certainly be expressed. A trait demonstrating this pattern is described as Mendelian inheritance. Nevertheless, in humans, hereditary expressions are not straightforward. Many of the person traits carry out not conform to the Mendelian pattern of inheritance. In this regard, they are described as non-Mendelian.

Homologous chromosomes Maternal chromosome head chromosome Inherited from the mommy Inherited indigenous the father Same hereditary sequence, loci, chromosomal length, and also centromere location Alleles might be the same or different

Pairing process

Meiosis is a type of cell department wherein diploid organisms halve their number of chromosomes and also homologous chromosomes pair up. In contrast, mitosis (another type of cabinet division) outcomes in 2 daughter cells, each containing the exact same chromosomal number together the parental cell. In meiosis, a diploid (2n) cabinet will give rise to four haploid (n) cells. The cells that undergo meiosis are the gametes creating haploid sperm cell and also egg cell. Haploidy is vital so that at fertilization the chromosomal number continues to be the exact same throughout generations. In order to accomplish haploidy, the cell undergoes two consecutive nuclear divisions. They are described as meiosis I and meiosis II. Come prepare the cell to meiosis, among the major preparatory measures is DNA replication. The chromosomes duplicate their DNA, particularly in the S phase of interphase. In ~ this point, every of the chromosomes will consist of 2 strands (sister chromatids) joined at the centromere. The pairing (synapse) the homologous chromosomes will occur at prophase I. DNA exchanges occur in between homologous chromosomes via homologous recombination and also crossover in ~ chiasmata between non-sister chromatids. Then, the homologous pairs line up in ~ the metaphase plate. Next, the homologous chromosomes separate throughout anaphase I and also move come the opposite poles that the cell. Then, the cabinet divides for the first time throughout telophase I leading to two gene non-identical daughter cells yet with sister chromatids still intact. Each cell will undergo meiosis II so the the result daughter cells will certainly each have actually a chromosomal number diminished by half.

Human karyotype


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The homologous chromosomes that humans based upon the gene sequences, loci, and also centromere location. A somatic cabinet (2n) contains 46 chromosomes and also 22 that them room homologous. If the sex chromosomes are both X chromosomes, climate the total number of homologous chromosomes is 23.

In humans, the nucleus generally contains 46 chromosomes. Thus, there are 22 bag of autosomes with approximately the exact same length, staining pattern, and also genes with the exact same loci. As for the sex chromosomes, the 2 X chromosomes are taken into consideration as homologous vice versa, the X and also Y chromosomes room not. Thus, females have actually 23 homologous chromosomes (i.e. 22 autosomes + 1 X-X chromosomes) vice versa, males have actually only 22.


Importance

The chromosomes are crucial to every living things due to the fact that they carry the hereditary instructions for all of the cell’s activities. They likewise bear the genetic information that determines the trait of one organism. Homologous chromosomes, therefore, are an essential in the exact same way. They bring genetic info that has been passed under from one generation come the next. And since alleles may possibly be various in the very same gene, the result is varying phenotypes. Thus, the distinctiveness that an separation, personal, instance of the same species is established. Except this, the biology is capable of reproducing offspring that is genetically various from itself and also from the rest of the descendants. The homologous chromosomes in the nucleus of the organism’s gamete pair up during meiosis. This event is vital to promote genetic variation. The homologous pair exchanges genes via genetic recombination therefore that hereditary diversity might be promoted. This is concerned as one of the advantages of having actually been able to reproduce sexually. Those that reproduce asexually produce a clone the themselves. Thus, this could reduce the gene pool. A small gene pool method low genetic diversity. It could be unfavorable because it method there is much less opportunity in gaining genes important for adapting come an environment prone to inexorable physicochemical changes. In contrast, greater hereditary variability way a higher propensity to obtain better genes. High genetic diversity also way a large gene pool. This, in turn, implicates boosted chances of gaining genes that could enhance organic fitness and survival.

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