What is Recombination: Definition and 64 Discussions

Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from the parents to the offspring. Most recombination is naturally occurring.
During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a section of genetic material is copied from one chromosome to another, without the donating chromosome being changed) (see SDSA pathway in Figure); or by the breaking and rejoining of DNA strands, which forms new molecules of DNA (see DHJ pathway in Figure).
Recombination may also occur during mitosis in eukaryotes where it ordinarily involves the two sister chromosomes formed after chromosomal replication. In this case, new combinations of alleles are not produced since the sister chromosomes are usually identical. In meiosis and mitosis, recombination occurs between similar molecules of DNA (homologous sequences). In meiosis, non-sister homologous chromosomes pair with each other so that recombination characteristically occurs between non-sister homologues. In both meiotic and mitotic cells, recombination between homologous chromosomes is a common mechanism used in DNA repair.
Gene conversion - the process during which homologous sequences are made identical also falls under genetic recombination.
Genetic recombination and recombinational DNA repair also occurs in bacteria and archaea, which use asexual reproduction.
Recombination can be artificially induced in laboratory (in vitro) settings, producing recombinant DNA for purposes including vaccine development.
V(D)J recombination in organisms with an adaptive immune system is a type of site-specific genetic recombination that helps immune cells rapidly diversify to recognize and adapt to new pathogens.

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  1. T

    I Microwave background radiation - temperature at recombination

    The commonly called value of the temperature at recombination is 3000 K. According to this reference the process of recombination can be described by the Saha equation: 3.1. Recombination and the formation of the CMB Recombination happens quickly (i.e., in much less than a Hubble time t ~...
  2. Buzz Bloom

    I Seeking reference for math related to the age of Recombination

    The Wikipedia references is https://en.wikipedia.org/wiki/Recombination_(cosmology). It says: Recombination occurred about 370,000 years after the Big Bang (at a redshift of z = 1100), and the cosmic background radiation is infrared [and some red] black-body radiation emitted when the universe...
  3. Mayan Fung

    I Recombination and open-circuit voltage in solar cells

    From the ideal diode model, we can derive the open-circuit voltage (Voc) as: $$ V_{oc} = \frac{nkT}{q} ln(\frac{I_L}{I_0} + 1) $$ where ##I_0## is the dark saturation current and ##I_L## is the light generated current. From the model, if the recombination rate increases, the dark saturation...
  4. TytoAlba95

    Biology MCQ: Genetics- Recombination in Drosophila

    Here (A) is a product of recombination between a-&-b, (B) is a product of recombination between b-&-c and (C) a parent 1. If 1000 is the total number of progenies, then 10% of it is 100 (A), 5% is 50 (B) and the rest should be <850 because the other parent has not been included. So I reject 1...
  5. TytoAlba95

    Recombination and intergenic distance

    Why is the chance of crossing over between two closely placed genes is considered low compared to those that are distantly placed on a chromosome? 'The frequency of recombinants produced by crossing over is the key to chromosome mapping. Fungal tetrad analysis has shown that, for any two...
  6. M

    B Age of the Universe at the recombination?

    The age of the universe at the recombination is reported everywhere on the internet as 379,000 years. I would be grateful if someone could point me towards the paper where this is calculated.
  7. Chromatic_Universe

    A Equilibrium recombination temperature for Helium

    How to get to the expression for equilibrium recombination temperature for Helium?
  8. WeiShan Ng

    I How Does Angular Diameter Distance Apply to the Last Scattering Surface?

    The definition of the angular diameter distance is the ratio of an object's physical transverse size to its angular size. However when I was reading my textbook, *Astrophysics in a Nutshell by Dan Maoz pp.220-221*, I am having some trouble trying to understand the notion of **angular diameter...
  9. Marcin H

    Semiconductors - Carrier Recombination

    Homework Statement A sample of Si at room temperature is doped with acceptors at a concentration of 3E16 cm^-3. An excess electron hole pair density of 1E14 cm^-3 is generated at some time t = 0. At t = 13.9 μs the excess EHP density is measured and found to be 5E13 cm^-3.(A). Does the initial...
  10. Mentz114

    I Can Spin State Recombination Restore the Original Quantum State?

    The picture shows an experimental setup where one or more silver atoms are sent from an oven through 3 Stern-Gerlag (SG) filters with outputs from E and F going to detectors. If C and D remain coherent they can recombine to restore the original state and the particles all go through port E. If...
  11. D

    Genetics double recombination counted twice in terms of RF

    When mapping out re-combinations of a crossed trihybrid you have to account for the proportion of the offspring who do not share parental genotypes. Of the 8 possible genotypes stemming from this mating, 6 will be recombinant and two will be of parental genotypes. Your idea is to Map out the...
  12. Jamison Bond

    HHO Easy Recombination to get electricity

    I was just wondering if there is an easy way to recombine hydrogen in a fuel cell style but effectively by doing electrolysis in reverse. Splitting is really easy but is there a way to get the HHO to recombine into water and release electricity effectively by reverse electrolysis? I get that...
  13. B

    Recombination Lines - Astrophysics

    Homework Statement For an atom X, the high-n levels have energies ##E_n = -\mu \frac{(\alpha c)^2}{n^2}## with ##\alpha = \frac{e^2}{\hbar c}## Find the frequency shift ##\nu_{Hen\alpha} - \nu_{Hn\alpha}## for ##n\alpha## giving a transition frequency near 142MHz (The notation here means...
  14. P

    I Why was the early universe opaque?

    I just learned from an Astronomy course that when the sub atomic particles were not bound together, they were moving around freely, but after the universe expanded and cooled, they began to combine to form Hydrogen atoms. Now, before this combination period, the photons couldn't pass through...
  15. S

    Reducing recombination losses in a semiconductor?

    I'm trying to understand recombination losses and ways to improve and reduce them in a standard crystalline silicon cell? I've been looking online for a while now but can't find any simple explanations. I understand recombination occurs when a conduction band electron loses energy and...
  16. E

    I Calculation of mean energy value of photons in recombination

    I am interested in the calculation of the mean energy value of CMB (Cosmic Microwave Background) photons from which the recombination is performed. The subject on French Wikipedia says : "Intuitively, one might say that recombination occurs when energy average of photons is of the order of the...
  17. newjerseyrunner

    B What causes recombination of virtual particles?

    In a situation like this: What causes the particle/antiparticle pair to recombine? They obviously will have opposite charge, is there a virtual photon being exchanged between them that's omitted from Feynman diagrams? That would imply that it's mathematically irrelevant, I know than these...
  18. Dr. Strange

    Question about Recombination Redshift values

    Wikipedia gives the redshift of recombination at z = 1500 (roughly 4,000 K). The Plank report list a 'redshift for which the optical length equals unity' and gives a value of 1090. What is the difference between the two?
  19. Benevito

    Photoluminescence at a heterojunction

    Do I understand it correctly that photoluminescence at a semiconductor heterojunction occurs because of intralayer recombination? If so, why can't photoluminescence occur because of interlayer recombination? Is it because momentum cannot be conserved in such a process ( like in the indirect gap...
  20. L

    What Drives the Evolution of Organism Variation?

    I am an evolutionary theoretician, focusing on the dynamics of process that shape the generation of variation in organisms, including properties such as mutational robustness, the evolution of evolvability, and modularity in the genotype-phenotype map. My main mathematical area is development...
  21. V

    Why does recombination in PN junctions release photons?

    In a pure crystal structure of some semiconductor compound each molecule is usually bound to other four by covalent bonds, in other words each of the four valence electrons of each molecule is in a covalent bond with another molecule. At 0K all electrons remain in these covalent bonds, but as...
  22. gracy

    Why Is There No Recombination in the F1 Generation?

    my question is why there is not any recombination in F1 generation?
  23. B

    Recombination of ion pairs in an ionization chamber

    What happens to the fill gas in an ionization chamber? Once incident radiation has created an ion pair, which has then moved to its opposite polarity electrode, is that ion pair removed from the fill gas? So if enough incident radiation is detected over a period of time all the gas would be...
  24. S

    Do charge carriers affect the total charge of a material in solid state physics?

    In solid state physics the "holes" usually regarded as an effective positive charge carriers. In order to have neutral charge some object needs to have an equal amount of protons and electrons. If some material such as an intrinsic semiconductor has equal amount of protons and electrons + some...
  25. J

    Recombination time for ionized atoms in a low pressure gas?

    I am looking into some new physics and had the following question come up: You have a neutral gas of let's say, CO atoms at 1 nanoTorr. An electron(s) comes passing through the gas ionizing only 1% of the gas atoms. How long does it take for the gas to come back to neutrality? In other words...
  26. V

    Hole current and Recombination

    Hello PFers! I hope everyone is doing well. Here's my question: The way I understand it (imperfectly, of course), forward-biasing a p-n junction diode, the electrons crossover from the n-type material and fall into the holes in the p-type material and then they are conducted through the holes...
  27. G

    Exploring the Mechanisms of Electron-Hole Recombination

    I understand that electron-hole produced when certain energy in form of a photons applied to atom that electron can escape. But, why would free electron fall back to the hole if it has more energy than energy on valence band? How recombination happens? Or it is because it collides with other...
  28. W

    How could inflation interact with recombination radiation?

    Okay, I will be the one in the class that asks the questions that some of us are afraid to ask but still want to know. How could the light from recombination, which occurred about 380K years after the Big Bang, interact with the gravitational waves generated from inflation, which occurred...
  29. V

    Recombination current in a p-n junction

    Hello all, I'm reading about rectification in a p-n junction. My book says there are two types of current for a p-n junction not in equilibrium: Generation current, and Recombination Current. Generation current Seems simple enough, but I don't get something about Recombination current. They...
  30. Y

    Why does indirect recombination have to indirectly go to two step

    for direct recombination, electrons go from up to down directly and vertically. However, for indirect recombination, it has to go through two-step process( go left and down) Here is my question. It makes sense to use for direct recombination, but why does indirect recombination have to...
  31. B

    Comparing 2-body & 3-body Recombination Rates

    Homework Statement Assume that recombination of atoms proceeds at the gas-kinetic rate of collisions. Compare the recombination rates for a 2-body and 3-body reaction, such as in the formation of O2. (hint: you may want to use production rate equations and calculate the number density of...
  32. P

    Help explaining the ion-electron recombination process

    I don't know the process in which a free electron finds its way back down to the ground state of a hydrogen ion and thus forming a neutral hydrogen atom. I have tried my hand at Googling the topic, but I can't seem to find any detailed websites about the electron-ion recombination for...
  33. Eagle9

    Calculating the amount of time for recombination

    Imagine that we have got some vessel under standard temperature and pressure filled with atomic Hydrogen inside and the electrons of these atoms have got the same spin and therefore they cannot join into Hydrogen molecules, so the process of recombination does not occur. But I was told that due...
  34. C

    Ions and Recombination: Exploring Effective Methods for Catalysts

    Is there any way to cataclyze the recombination of oppositely charged ions? I'm wondering if an effective method exists. Thanks all!
  35. E

    How to find scale factor at recombination?

    If we know that the temperature of photons was apprx. 3000 K at recombination and the temperature of the CMB is apprx. 2.725 K today, how can we extrapolate the value of the scale factor at recombination? I know that recombination happens at a matter-dominated era, such that the density goes...
  36. C

    Preventing recombination in a diffusion cloud chamber?

    Hello all, I built an expansion cloud chamber and noted that an electrostatic field was needed to see the ionizing radiation. I know this is needed to prevent recombination of the ions and their free electrons. However, I built a diffusion cloud chamber a while ago that called for no electric...
  37. D

    What is a recombination ionization chamber?

    I have been under the impression that recombination is a bad thing, not a good thing. And you increase your voltage on an ion chamber until recombination is eliminated. I also understand that recombination is a bigger problem for neutron and alpha radiation because its ionization trail is much...
  38. L

    Excitons. Is this the same as radiative recombination?

    Hi, I'm having difficulty getting my head round the concept of excitons, which have recently been introduced into my Uni course. Previously, I've always understand the operation of LEDs as follows: Under forward bias, electron and holes are injected and recombine at the p-n junction...
  39. T

    Independent Assortment & Crossing Over: Genetic Recombination

    1. When crossing over does not occur, how many possible chromosome combination can result from independent assortment of the homologous chromosomes? I believe it is 4, because we have 4 identical chromosomes. Is this correct? 2. How does this change when crossing over occurs? It increases or...
  40. 2

    What Triggers Electron-Hole Recombination in Semiconductors?

    Hello, This is about a direct band gap semiconductor: Q1) What induces recombination of an electron in the conduction-band with a hole in the valence-band? Is it the electrostatic attraction between a negatively charged electron and a positively charged hole which induces recombination or...
  41. P

    SRH and radiative recombination

    Hi, I have read in different references that trap assisted SRH recombination is non radiative and gives the energy to phonons. However, I have not been able to understand why is not possible to generate photons in this case. I mean, can SRH recombination give the energy to photons? What...
  42. M

    Why the process of recombination is called re combination?

    Why the process of recombination is called "re"combination? The process in which the nucleus and electrons combined to form neutral atoms at early times is called recombination. But why it is added an "re" to "combination"? Is there any combination process before this process? Thx!
  43. B

    Mitochondrial DNA and recombination

    Does mtDNA recombine? I've tried doing my own research but I'm getting very mixed responses, from the evidence being strongly against it, right up to it being a well-known phenomenon in yeast. any insight please?
  44. S

    Recombination Freq.: Genetic Mapping Hwk Problem

    Homework Statement The recombination frequency between gene “Q” and gene “Z” is found to be 23.5%. The recombination frequency between “Q” and a third gene “R” is 10%. The frequency of recombination between “Z” and “R” is 13.5%. Which one of the following is NOT true concerning these three...
  45. S

    Understanding Recombination Frequencies: Distance Between Genes Explained

    Confused on 2 questions here If a recombination frequency between two genes is 1.5%, what is the distance between the genes in map units on the linkage map? a. Impossible to determine, because the interference is not known. b. 1.5 c. 3 d. 0.75 Recombination frequencies a. arise...
  46. S

    Biology How Do Recombination Frequencies Relate to Gene Distance?

    Confused on 2 questions hereIf a recombination frequency between two genes is 1.5%, what is the distance between the genes in map units on the linkage map? a. Impossible to determine, because the interference is not known. b. 1.5 c. 3 d. 0.75 Recombination frequencies a. arise from completely...
  47. R

    What Is the Surface Recombination Velocity of an N-Type Silicon Sample?

    "An n-type silicon sample has 2x10^16 arsenic atoms/cm3, 2x10^15 bulk recombination centers/cm3, and 10^10 surface recombination centers/cm2. (a) Find the bulk minority carrier lifetime, the diffusion length, and the surface recombination velocity under low-injection conditions. The values...
  48. N

    Base current in transistor flows due to recombination of electrons

    base current in transistor flows due to recombination of electrons and holes. Explain
  49. F

    Which Catalyst Can Slow Bubble Formation in Electroosmotic Pumps?

    Hello everybody! I am working on bubble formation issue in electroosmotic pumps. Those bubble are formed by water electrolysis on platinium electrode and I am searching for catalyst for water recombination compatible with biological applications to at least slow down the bubble formation...
  50. S

    Surface recombination velocity of electron

    at the metal semiconductor contact the transport of minority carriers is describe by surface recombination velocity, what s the surface recombination velocity for electron and hole at the same contact?