n., plural: homologous chromosome
Definition: one of two chromosomes with the same gene sequence, loci, chromosome length, and centromere position
ONEchromosome homologuesrefers to one of the twochromosomeswith the same gene sequence, loci, chromosomal length and centromere position. A homologous pair consists of a paternal and maternal chromosome. In humans, there are a total of 46 chromosomes in the cell nucleus of a body cell. Half of them (22 autosomes + X or Y chromosome) are inherited from the father and the other half (22 autosomes + X chromosome) from the mother. Each maternal chromosome has a corresponding paternal chromosome; They mate duringMeiosis🇧🇷 Normally, a female has 23 homologous chromosomes, while a male has 22. This is because the X and Y sex chromosomes are not homologous in males. The pairing of homologous chromosomes during meiosis is important for promoting genetic variation. Due to the genetic recombination that occurs between homologous pairs in meiosis, the resulting haploid gametes contain chromosomes that are genetically distinct from one another. This multiplies the gene pool, thereby increasing the chances of acquiring genes essential for biological fitness and survival.
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Definition of homologous chromosome
In biology, chromosomes are homologouspairedchromosomes. They have essentially the same gene sequence, loci (gene position), centromere position, and chromosome length. Although they may have the same genetic sequence and loci, they may differalleles🇧🇷 The homologous pair consists of a paternal and maternal chromosome. These chromosomes pair up duringMeiosisbut not duringMitosis.
The termcounterpartcame from the Greekcounterpart, which means "agree" or "unified". It's a combination ofAlegre, means “same” andlogos, which means "relationship". The termchromosomewas coined in 1889 by the German anatomist Wilhelm von Waldeyer-Hartz. It was derived from the GreekChrom, which means "color", as it can be easily colored with basic dyes. Synonym: counterpart.
Homologous chromosome vs. heterologous chromosome
if there are chromosomescounterpart, it means they aresame, at least in terms of gene sequences and loci.heterologousbasically means "different". This means that heterologous (non-homologous) chromosomes would belong to any two chromosomesandersB. in relation to gene sequence and loci. During meiosis, homologous chromosomes can naturally exchange genetic material. Heterologous chromosomes do not. However, there are cases where heterologous chromosomes exchange parts of chromosomes. When this occurs, the process is invokedchromosomaltranslocation🇧🇷 It's a way ofMutationthat can lead to severe chromosomal aberrations. For the comparison between homologous and heterologous chromosomes, see Table 1.
Table 1: Differences between homologous and heterologous chromosomes
|Homologous chromosomes have alleles on the same genes located at the same loci.||Heterologous chromosomes have alleles on different genes.|
|Mating During Meiosis||Does not mate during meiosis|
|Gene exchange can occur at synapses.||Gene exchange can occur during translocation.|
|Basic parts: ||Basic parts: |
|Examples: ||Examples: |
Homologous chromosomes vs sister chromatids
In meiosis, each of the homologous chromosomes consists of two identical chromatids linked by a common chromatid.Kinetochor(Centromere). Identical chromatids are specifically namedsister chromatidsto protect them from the so-calledno sisterchromatids. Before cell division, the chromosomes in the cell nucleus appear as thread-like filaments (so-calledchromatin🇧🇷 When a cell is destined to undergo mitosis or meiosis, it condenses into thicker structures. At this point, the chromatin is called a chromosome. The DNA in the chromosome replicates itself through DNA replication during the S phase of the chromosomeintermediate phase🇧🇷 After replication, there would be two copies of DNA, each present on a strand called a chromatid. The two chromatids connected by a common centromere are called sister chromatids. The chromatids of the other member of a homologous pair are called non-sister chromatids.
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It ischromosomesof a eukaryotic cell are located in the nucleus of the cell. The chromosomes in the nucleus of the cell consist of two sets. One set would come from the male gamete (sperm cell) and the other set would come from the female gamete (egg cell). beforefertilizationboth gametes are haploid. If the sperm successfully fertilizes the egg, the resulting zygote is diploid, meaning that the union of the two haploid cells results in a single cell with two sets of chromosomes: one set that comes from the mother and one that comes from the mother. dad . Each maternal chromosome has a corresponding paternal chromosome with the same gene sequence, gene loci, chromosomal length, and centromere position. The pair become close during meiosis so they can exchange genes between sister and non-sister chromatids.
Although both members of the homologous pair have similar genes and loci, they can differ in their genes.alleles🇧🇷 For example, they both carryGeneCoding for the eye color trait. One has alleles for the brown-eyed trait, while the other is for the blue-eyed trait. In this case, the alleles are different and the homologous chromosomes are described asheterozygous🇧🇷 On the contrary, if the alleles are the same (for example, both alleles for the same genetic code for the trait blue eyes), they are said to behomozygous🇧🇷 The importance of alleles was explored by Gregor Mendel through his seminal work onGeneticUse of peas. He was able to show that one of the alleles can be dominant over the other. In this case, only one allele is expressed. A feature that shows this pattern is called amendelian legacy🇧🇷 However, gene expressions in humans are not straightforward. Many human traits do not match the Mendelian pattern of inheritance. In this context, they are callednot Mendelian.
|maternal chromosome||paternal chromosome|
|inherited from mother||inherited from the father|
|Same genetic sequence, loci, chromosome length and centromere position|
|Alleles can be the same or different|
MeiosisIt is a form of cell division in which diploid organisms halve their number of chromosomes and homologous chromosome pairs. In contrast, mitosis (another form of cell division) results in two daughter cells, each containing the same number of chromosomes as the parent cell. During meiosis, one diploid (2n) cell gives rise to four haploid (n) cells. The cells that undergo meiosis are gametes, which produce haploid sperm and eggs.Haploidyit is important for the number of chromosomes to remain the same across generations during fertilization. To achieve haploidy, the cell undergoes two consecutive nuclear divisions. They are referred to asMeans IeMeiosis II🇧🇷 To prepare the cell for meiosis, one of the most important preparatory steps is DNA replication. Chromosomes duplicate their DNA, particularly in the S phase of interphase. At this point, each of the chromosomes consists of two strands (sister chromatids) joined at the centromere. Pairing (synapsis) of homologous chromosomes occurs in prophase I. Exchange of DNA occurs between homologous chromosomeshomologous recombinationecrossingin chiasms between non-sister chromatids. Then the homologous pairs line up on the metaphase plate. Then, during anaphase I, the homologous chromosomes separate and move to opposite poles of the cell. The cell then divides for the first time during telophase I, resulting in two daughter cells that are genetically non-identical but have sister chromatids still intact. Each cell undergoes meiosis II, so that the resulting daughter cells each have a number of chromosomes halved.
In humans it isKernnormally contains 46 chromosomes. So there are 22 pairscarssomewith approximately the same length, the same coloration pattern and genes with the same loci. As for the sex chromosomes, the twoX-chromosomeare considered homologous, while the X and Y chromosomes are not. Thus, females have 23 homologous chromosomes (i.e. 22 autosomes + 1 X-X chromosome), while males have only 22.
Chromosomes are vital for everyoneCreaturebecause they carry the genetic instructions for all cellular activities. They also carry the genetic information that determines a person's trait.Body🇧🇷 Homologous chromosomes are therefore equally vital. They carry genetic information passed from one generation to another. And because the alleles on the same gene can be different, different phenotypes result. Thus, the distinction of an individual of the same species is established. Furthermore, the organism is capable of reproducing offspring that are genetically different from itself and the rest of the offspring. The homologous chromosomes in the nucleus of the organism's gametes pair up during meiosis. This event is crucial for encouraging genetic variation. The homologous pair exchanges genes by genetic recombination so that genetic diversity can be promoted. This is considered one of the benefits of being able to reproduce sexually. Those that reproduce asexually create a clone of themselves, which can reduce the gene pool. A small gene pool means low genetic diversity. It may be unfavorable because there are fewer opportunities to acquire genes essential for adaptation to an environment vulnerable to relentless physicochemical changes. In contrast, greater genetic variability means greater propensity to buyBestgenes High genetic diversity also means highgeneration pool🇧🇷 This, in turn, implies greater chances of acquiring genes that can improve biological fitness and survival.
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Try taking the quiz below to check what you've learned so far about homologous chromosomes.
What is homologous chromosome in biology? ›
What are Homologous Chromosomes? Homologous Chromosomes are made of chromosomal pairs of the same length and centromere positions for the genes corresponding to the same loci. Typically one of the chromosomes is inherited from the father and the other from the mother.What is homologous chromosome a short definition? ›
The chromosomal pair which contains the maternal as well as the paternal chromatid of the same length and gene position, and are joined by the centromere is referred to as a homologous chromosome.What is homologous with example? ›
having the same or a similar relation; corresponding, as in relative position or structure. corresponding in structure and in origin, but not necessarily in function: The wing of a bird and the foreleg of a horse are homologous. having the same alleles or genes in the same order of arrangement: homologous chromosomes.What is a homologous simple definition? ›
: having the same relative position, value, or structure: such as. (1) biology : exhibiting biological homology. (2) biology : having the same or allelic genes with genetic loci usually arranged in the same order.What is homologous chromosome quizlet? ›
Homologous chromosomes are chromosome pairs, one from each parent, that are similar in length, gene position and centromere location. Homologous chromosomes are two sister chromatids stuck together with cohesions forming a tetrad.What is an example of a homologous gene? ›
A homologous gene is a type of gene that is inherited by two different species that evolved from the same ancestor. Both the house cat and a leopard share a common ancestor. Similarly, both wooly mammoth and the elephant share a common ancestor. Thus, these species contain homologous genes.What is the best definition of homologous structure? ›
Homologous structures are similar physical features in organisms that share a common ancestor, but the features serve completely different functions. An example of homologous structures are the limbs of humans, cats, whales, and bats.What are homologous chromosomes chegg? ›
Homologous chromosomes are two sets of the DNA that is present in the nucleus of the cell and contain the same genes, each from one of the parental DNA. In simpler terms, a person has 23 pairs of chromosomes, which is 46 in number.Which of the following statements best describes homologous chromosomes? ›
Which of the following statements best describes homologous chromosomes? Chromosomes that have the same genes in the same position and are the same size and shape.What is a good example of a homologous structure? ›
A common example of homologous structures in evolutionary biology are the wings of bats and the arms of primates. Although these two structures do not look similar or have the same function, genetically, they come from the same structure of the last common ancestor.
Which two are an example of a homologous structure? ›
Examples of homologous structures include the wings of bats and the hands of human, as both these types of animals have evolved from a shared ancestor, but the aforementioned structures have very different functions.What does homologous mean quizlet? ›
Terms in this set (24)
Homologous. Structures that have different mature forms but develop from the same embryonic tissues. Analogous. corresponding in function but not in evolutionary origin. Divergent.
Homologous structures are organs or skeletal elements of animals and organisms that, by virtue of their similarity, suggest their connection to a common ancestor. These structures do not have to look exactly the same, or have the same function.Why are homologous chromosomes? ›
The two chromosomes in a homologous pair are very similar to one another and have the same size and shape. Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations. However, they don't necessarily have the same versions of genes.What are homologous chromosomes quizlet Chapter 13? ›
Homologous chromosomes contain the same genes but often different alleles. Sister chromatids contain the same genes and the same alleles.What is a homologous chromosome in meiosis? ›
Homologous chromosomes are matched pairs containing the same genes in identical locations along their length. Diploid organisms inherit one copy of each homologous chromosome from each parent; all together, they are considered a full set of chromosomes.What is an example of homology in biology? ›
An example of homologous characters is the four limbs of tetrapods. Birds, bats, mice, and crocodiles all have four limbs. Sharks and bony fish do not. The ancestor of tetrapods evolved four limbs, and its descendents have inherited that feature — so the presence of four limbs is a homology.What are 3 characteristics of homologous chromosomes? ›
Homologous chromosomes are chromosomes that share: The same structural features (e.g. same size, same banding patterns, same centromere positions) The same genes at the same loci positions (while the genes are the same, alleles may be different)What are the 4 homologous chromosomes called? ›
Each pair of chromosomes—called a tetrad, or a bivalent—consists of four chromatids. At this point, the homologous chromosomes exchange genetic material by the process of crossing over (see linkage group).Do homologous chromosomes have the same genes? ›
The chromosomes in a homologous pair each have the same genes in the same order, but there may be variation between them, resulting in different alleles. Some of the variants in these alleles might have functional implications while others will not.
Do homologous chromosomes carry information for the same traits? ›
Homologous chromosomes are the same size and shape and carry information to make the same proteins and determine the same traits. Humans have 23 pairs of homologous chromosomes (23 from Ma and 23 from Pa); each species has its own chromosome number.Are homologous chromosomes inherited from the same parent? ›
Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the organism's mother; the other is inherited from the organism's father.What is an example of homologous structures quizlet? ›
Examples of homologous structures are the bones of a cat's leg, bird's wing, whale's flipper and a human arm. They are homologous because they formed from the same embryonic tissue but developed into different mature structures.What is true of homologous chromosomes? ›
Homologous chromosomes are matched pairs containing genes for the same traits in identical locations along their length. Diploid organisms inherit one copy of each homologous chromosome from each parent; all together, they are considered a full set of chromosomes.What is homologous structure in biology quizlet? ›
Homologous structure. Structures that are similar in different species of common ancestry. Vestigial structure. A structure that is present in an organism but no longer serves its original purpose. Inherited.What are 3 homologous structures? ›
A dolphin's flipper, a bird's wing, a cat's leg, and a human arm are considered homologous structures.What are the types of homologous? ›
Dependent on the level of comparison four types of homology are defined: ( 1) Iterative ( = serial = homonomy), (2) ontogenetic, (3) di- or polymor- phic, and (4) supraspecific homology. The significance of all four types for evolutionary biology and phylogenetic analysis is outlined.What are homologous structure answers? ›
HOMOLOGOUS STRUCTURES (definition): similar structures that related organisms share from a common ancestor. Analogous structures have very different anatomies but. similar functions. These are seen in organisms that are not. necessarily closely related, but live in similar environments.What is a sentence for homologous? ›
A pair of homologous genes sampled from two species must have diverged in the ancestral species.Why is it called homologous? ›
These are homologous chromosomes, because they carry the same genes. However, they can carry different alleles of each gene, shown by their internal pattern. This organism can reproduce asexually, simply by duplicating the DNA and dividing the cell.
What is the role of a homologous chromosome? ›
Homologous chromosomes are important in the processes of meiosis and mitosis. They allow for the recombination and random segregation of genetic material from the mother and father into new cells.How do you identify homologous chromosomes? ›
The two chromosomes in a homologous pair are very similar to one another and have the same size and shape. Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations.What contains homologous chromosomes? ›
A homologous pair consists of one paternal and one maternal chromosome. In humans, there are a total of 46 chromosomes in the nucleus of a somatic cell. Half of them (22 autosomes + X or Y chromosome) are inherited from the father and the other half (22 autosomes + X chromosome), from the mother.Which is true of homologous chromosomes? ›
A homologous chromosome is a pair of identical chromosomes that is present in a diploid (2n) organism. The homologous chromosomes contain the same genes.
Homologous chromosomes correspond to the chromosomes present on the same pair in contrast to non-homologous chromosomes where they are found on different pairs. Number of chromosomes in homologous pairs are based on the ploidy of that entity.How many homologous chromosomes are there? ›
There are 23 pairs of homologous chromosomes, or homologues, in each cell. After replication there are a total of 92 sister chromatids in each cell. There are 46 individual chromosomes in each cell.Where are homologous chromosomes found? ›
In each somatic cell of the organism (all cells of a multicellular organism except the gametes or reproductive cells), the nucleus contains two copies of each chromosome, called homologous chromosomes.Do homologous chromosomes determine gender? ›
A human male has two sex chromosomes, the X and the Y. Unlike the 44 autosomes (non-sex chromosomes), the X and Y don't carry the same genes and aren't considered homologous. Instead of an X and a Y, a human female has two X chromosomes. These X chromosomes do form a bona fide homologous pair.What are 4 examples of homologous structures? ›
A dolphin's flipper, a bird's wing, a cat's leg, and a human arm are considered homologous structures.Which is the best description of homologous chromosomes? ›
Which of the following describes homologous chromosomes most accurately? Chromosomes that have been inherited from both the parents and which have the same genes arranged in the same order.
What are 3 examples of homologous structures? ›
The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale are homologous structures. They are different and have a different purpose, but they are similar and share common traits.