homologous

American  

[huh-mol-uh-guhs, hoh-] / həˈmɒl ə gəs, hoʊ- /

adjective

1. having the same or a similar relation; corresponding, as in relative position or structure.

2. corresponding in structure and in origin, but not necessarily in function.

   The wing of a bird and the foreleg of a horse are homologous.

3. having the same alleles or genes in the same order of arrangement.

   homologous chromosomes.

4. Chemistry. of the same chemical type, but differing by a fixed increment of an atom or a constant group of atoms.

   Methyl and ethyl alcohols are homologous.

5. Immunology. pertaining to an antigen and its specific antibody.

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homologous British  

/ ˌhɒm-, həʊˈmɒləɡəs, hɒ-, ˌhəʊməˈlɒdʒɪkəl /

adjective

1. having a related or similar position, structure, etc

2. chem (of a series of organic compounds) having similar characteristics and structure but differing by a number of CH 2 groups

3. med

   1. (of two or more tissues) identical in structure

   2. (of a vaccine) prepared from the infecting microorganism

4. biology (of organs and parts) having the same evolutionary origin but different functions Compare analogous

   the wing of a bat and the paddle of a whale are homologous

5. maths (of elements) playing a similar role in distinct figures or functions

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homologous Scientific  

/ hə-mŏl′ə-gəs /

1. Similar in structure and evolutionary origin but having different functions, as a human's arm and a seal's flipper.

2. Being one of a pair of chromosomes, one from the female parent and one from the male parent, that have genes for the same traits in the same positions. Genes on homologous chromosomes may not have the same form, however. For example, one chromosome in a pair of homologous chromosomes may contain a gene for brown eyes, and the other a gene for blue eyes. Human females have 23 pairs of homologous chromosomes (including the two X chromosomes), while human males have 22 because the Y chromosome is not paired.

3. Belonging to or being a series of organic compounds, each successive member of which differs from the preceding member by a constant increment, especially by an added CH ₂ group. The alkanes (methane, ethane, propane, and others) are a homologous series of compounds.

4. Involving organisms of the same species, as in grafted body tissues.

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Usage

What does homologous mean? Homologous is used to describe multiple things that are the same or similar, especially in structure or origin. In science, homologous is most often used in the phrase homologous structures, which refers to body parts of animals that have a similar structure or origin, as in The arms of humans and the limbs of cats are homologous structures—the layout of the bones is very similar.  Homologous structures may have different functions. For example, a human arm and a bat’s wing are considered homologous structures because they have the same bone structure, even though they obviously have different functions. In biology, the presence of similarities like this is known as homology. Homologous structures are the opposite of analogous structures, which refers to body parts that serve similar functions but have different structures or origins. For example, both birds and wasps have wings, but their wings have different appearances and consist of different parts and evolved from different origins. Example: A horse’s leg and a whale’s flipper are homologous structures that evolved from the same origin.

Other Word Forms

• homologically adverb
• nonhomologous adjective
• unhomologous adjective

Etymology

Origin of homologous

1650–60; < Medieval Latin homologus < Greek homólogos agreeing, equivalent to homo- homo- + -logos proportional, equivalent to log- (stem of lógos proportion; logos ) + -os -ous

Explanation

Something homologous is similar in function to something else. You might say that your dog's hind legs and your legs are homologous, because they have similar structure and function. Homologous comes from the Latin for "agreeing," and has the root homo- in it, which means "same." In biology, homologous either refers to traits that share an origin, and have the same function (like the spine on all vertebrates), or structures that share an evolutionary origin, but have developed different functions. Either way, something is the same about them. You'll also find homologous in math, like when two triangles share a line.

Example Sentences

Worth noting, this work presents the first homologous series based on defect ordering found for hybrid organic-inorganic perovskites.

From Science Daily • Apr. 17, 2024

When meiosis begins, homologous chromosomes arrange themselves into elongated structures organized along a backbone called the axis.

From Science Daily • Jan. 4, 2024

The homologous pairs have matching genes arranged in the same order, with small variations within the genes -- these are the variations that make each individual unique.

From Science Daily • Jan. 4, 2024

Visit this interactive site to guess which bones structures are homologous and which are analogous. There are also examples of evolutionary adaptations that illustrate these concepts.

From Textbooks • Jan. 1, 2015

It has recently been reported that the nucleic acid of chloroplasts is, in fact, homologous with that of certain photosynthetic microorganisms.

From "The Lives of a Cell" by Lewis Thomas