A homologous chromosome comes to one that a pair the chromosomes v the very same gene sequence, loci, chromosomal length, and also centromere location. A homologous pair is composed of one paternal and one maternal chromosome. In humans, there are a total of 46 chromosomes in the cell core of a somatic cell. Half of lock (22 autosomes + X or Y chromosome) room inherited native the father and also the other fifty percent (22 autosomes + X chromosome), native the mother. Every maternal chromosome has actually a corresponding paternal chromosome; castle pair up throughout meiosis. Typically, a woman will have actually 23 homologous chromosomes vice versa, a masculine will have actually 22. The is because the sex chromosomes, X and Y, in males space not homologous. The pairing increase of homologous chromosomes during meiosis is essential to promote genetic variation. Due to the fact that of the hereditary recombination the occurs in between homologous pairs at meiosis, the result haploid gametes contain chromosomes that are genetically different from every other. This amplifies gene pool, thereby, increasing the opportunities of obtaining genes crucial to biological fitness and survival.

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Homologous chromosome definition

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


Etymology

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

Homologous chromosomes vs. Heterologous chromosomes

When chromosomes are homologous, it means that they space the same, at least in terms of the gene sequences and also loci. Heterologous, in essence, method “different”. This means that heterologous (non-homologous) chromosomes would, therefore, pertain to any type of two chromosomes that are different, such together in regards to gene sequence and loci. Throughout meiosis, homologous chromosomes might naturally exchange hereditary material. Heterologous chromosomes do not. However, there space instances wherein heterologous chromosomes execute exchange chromosomal parts. Once this occurs, the process is called chromosomal translocation. It is a type 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 top top the same genes situated in the same loci. Heterologous chromosomes have actually alleles on various genes.
Pairs up throughout meiosis Does no pair up throughout meiosis
Gene exchanges may take place at synapse. Gene exchanges may take place at translocation.
Basic parts:

centromere (kinetochore) long arms (q) short arms (p)
Basic parts:

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

22 autosomal chromosomes XX sex chromosomes
Examples:

XY sex chromosome any chromosome the supposedly belongs come a chromosomal pair

Homologous chromosome vs. Sister chromatids

At meiosis, each of the homologous chromosomes is consisted of of two similar chromatids joined together by a common kinetochore (centromere). The similar chromatids are specifically called sister chromatids to differentiate them native the so-called non-sister chromatids. Before cell divisions, the chromosomes in the nucleus appear as threadlike strands (called chromatins). As soon as a cell is fated to undergo mitosis or meiosis, castle condense right into thicker structures. By this time, the chromatin is referred to as a chromosome. The DNA in the chromosome replicates by DNA replication during the S phase of the interphase. After replicating, there would have been 2 DNA copies, each existing in a strand called chromatid. The 2 chromatids join by a typical centromere are described as sister chromatids. The chromatids of the various other member the a homologous pair are described as non-sister chromatids.


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Homologous chromosomes showing sister and also non-sister chromatids. Hereditary recombination have the right to occur in between non-sister chromatids.

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Characteristics

The chromosomes that a eukaryotic bio cell are located in the nucleus. The chromosomes in the nucleus space of two sets. One collection would come native the male gamete (sperm cell) and also the various other set, from the mrs gamete (egg cell). Before fertilization, both gametes are haploid. As soon as the sperm cell properly fertilizes the egg cabinet the resulting zygote is a diploid, which means the union the the two haploid cells outcomes in a solitary cell through two set of chromosomes: one collection that is maternally-derived and another collection that is paternally-derived. Each maternal chromosome has actually a corresponding paternal chromosome of the very same gene sequence, gene loci, chromosomal length, and also centromere location. The pair comes close to each other during meiosis so the they could exchange genes between sister and non-sister chromatids. Back both members that the homologous pair have comparable genes and also loci, they may differ in the alleles. Because that example, both the them lug genes coding because that the eye shade trait. One has alleles for the brown-eye characteristics 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 are the exact same (e.g. Both alleles for the very same gene password for the blue-eye trait) then, they are stated to it is in homozygous. The significance of alleles to be demonstrated by Gregor Mendel v his pioneering works in genetics using garden peas. He was able to display that one of the alleles might be dominant over the other. In this case, only one allele will certainly be expressed. A characteristics demonstrating this pattern is described as Mendelian inheritance. Nevertheless, in humans, hereditary expressions are not straightforward. Plenty of of the person traits carry out not conform come the Mendelian pattern of inheritance. In this regard, lock are described as non-Mendelian.

Homologous chromosomes Maternal chromosome paternal chromosome Inherited native the mother Inherited native the father Same hereditary sequence, loci, chromosomal length, and also centromere place Alleles may be the exact same or various

Pairing process

Meiosis is a kind of cell division wherein diploid organisms halve their number of chromosomes and also homologous chromosomes pair up. In contrast, mitosis (another type of cabinet division) outcomes in two daughter cells, every containing the very same chromosomal number together the parental cell. In meiosis, a diploid (2n) cabinet will provide rise to four haploid (n) cells. The cells the undergo meiosis room the gametes creating haploid sperm cell and egg cell. Haploidy is important so the at fertilization the chromosomal number continues to be the same throughout generations. In stimulate to accomplish haploidy, the cell undergoes 2 consecutive nuclear divisions. Castle are described as meiosis I and also meiosis II. Come prepare the cell to meiosis, among the significant preparatory measures is DNA replication. The chromosomes duplicate your DNA, an especially in the S phase of interphase. In ~ this point, every of the chromosomes will consist of 2 strands (sister chromatids) join at the centromere. The pairing (synapse) that homologous chromosomes will take place at prophase I. DNA exchanges occur between homologous chromosomes via homologous recombination and also crossover in ~ chiasmata between non-sister chromatids. Then, the homologous pairs heat up in ~ the metaphase plate. Next, the homologous chromosomes separate during anaphase I and also move come the the opposite poles the the cell. Then, the cabinet divides because that 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 resulting daughter cells will certainly each have actually a chromosomal number lessened by half.

Human karyotype


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

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


Importance

The chromosomes are necessary to all living things due to the fact that they bring the hereditary instructions for every one of the cell’s activities. They additionally bear the genetic information that determines the properties of one organism. Homologous chromosomes, therefore, are an essential in the very same way. They bring genetic info that has been passed under from one generation to the next. And since alleles may possibly be various in the same gene, the result is differing phenotypes. Thus, the distinctiveness the an individual of the same types is established. Except this, the organism is capable of reproducing offspring that is genetically different from itself as well as from the rest of its descendants. The homologous chromosomes in the cell nucleus of the organism’s gamete pair up throughout meiosis. This event is an essential to promote hereditary variation. The homologous pair exchanges gene via genetic recombination therefore that genetic diversity may be promoted. This is related to as among the benefits of having actually been able to reproduce sexually. Those the reproduce asexually produce a clone the themselves. Thus, this can reduce the gene pool. A little gene pool way low hereditary diversity. It can be unfavorable since it way there is much less opportunity in getting genes crucial for adapting to an setting prone come inexorable physicochemical changes. In contrast, greater genetic variability method a greater propensity to acquire better genes. High genetic diversity also means a huge gene pool. This, in turn, implicates enhanced chances of acquiring genes that can enhance organic fitness and survival.

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