Question: What does genetic recombination do?
About the article "Evolution", section "Genetic hitchhiking".

Candidate passages:
In genetic engineering, recombination can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA.
A prime example of such a use of genetic recombination is gene targeting, which can be used to add, delete or otherwise change an organism's genes.
This technique is important to biomedical researchers as it allows them to study the effects of specific genes.
Techniques based on genetic recombination are also applied in protein engineering to develop new proteins of biological interest. 
Mitochondria divide by binary fission, similar to bacterial cell division.
The regulation of this division differs between eukaryotes.
In many single-celled eukaryotes, their growth and division is linked to the cell cycle.
For example, a single mitochondrion may divide synchronously with the nucleus.
This division and segregation process must be tightly controlled so that each daughter cell receives at least one mitochondrion.
In other eukaryotes (in mammals for example), mitochondria may replicate their DNA and divide mainly in response to the energy needs of the cell, rather than in phase with the cell cycle.
When the energy needs of a cell are high, mitochondria grow and divide.
When the energy use is low, mitochondria are destroyed or become inactive.
In such examples, and in contrast to the situation in many single celled eukaryotes, mitochondria are apparently randomly distributed to the daughter cells during the division of the cytoplasm.
Understanding of mitochondrial dynamics, which is described as the balance between mitochondrial fusion and fission, has revealed that functional and structural alterations in mitochondrial morphology are important factors in pathologies associated with several disease conditions.
An individual's mitochondrial genes are not inherited by the same mechanism as nuclear genes.
Typically, the mitochondria are inherited from one parent only.
In humans, when an egg cell is fertilized by a sperm, the egg nucleus and sperm nucleus each contribute equally to the genetic makeup of the zygote nucleus.
In contrast, the mitochondria, and therefore the mitochondrial DNA, usually come from the egg only.
The sperm's mitochondria enter the egg but do not contribute genetic information to the embryo.
Instead, paternal mitochondria are marked with ubiquitin to select them for later destruction inside the embryo.
The egg cell contains relatively few mitochondria, but it is these mitochondria that survive and divide to populate the cells of the adult organism.
Mitochondria are, therefore, in most cases inherited only from mothers, a pattern known as maternal inheritance.
This mode is seen in most organisms including the majority of animals.
However, mitochondria in some species can sometimes be inherited paternally.
This is the norm among certain coniferous plants, although not in pine trees and yew trees.
For Mytilidae mussels paternal inheritance only occurs within males of the species.
It has been suggested that it occurs at a very low level in humans.
There is a recent suggestion mitochondria that shorten male lifespan stay in the system because mitochondria are inherited only through the mother.
By contrast natural selection weeds out mitochondria that reduce female survival as such mitochondria are less likely to be passed on to the next generation.
Therefore it is suggested human females and female animals tend to live longer than males.
The authors claim this is a partial explanation.
Uniparental inheritance leads to little opportunity for genetic recombination between different lineages of mitochondria, although a single mitochondrion can contain 2–10 copies of its DNA.
For this reason, mitochondrial DNA usually is thought to reproduce by binary fission.
What recombination does take place maintains genetic integrity rather than maintaining diversity.
However, there are studies showing evidence of recombination in mitochondrial DNA.
It is clear that the enzymes necessary for recombination are present in mammalian cells.
Further, evidence suggests that animal mitochondria can undergo recombination.
The data are a bit more controversial in humans, although indirect evidence of recombination exists.
If recombination does not occur, the whole mitochondrial DNA sequence represents a single haplotype, which makes it useful for studying the evolutionary history of populations. 
Because genetic recombination between two markers is detected only if there are an odd number of chromosomal crossovers between the two markers, the distance in centimorgans does not correspond exactly to the probability of genetic recombination.
Assuming Haldane's map function, where the number of chromosomal crossovers is according to a Poisson distribution, a genetic distance of "d" centimorgans will lead to an odd number of chromosomal crossovers, and hence a detectable genetic recombination, with probability formula_1 formula_2 where "sinh(·)" is the hyperbolic sine function.
The probability of recombination is approximately "d"/100 for small values of "d" and approaches 50% as "d" goes to infinity.
The formula can be inverted, giving the distance in centimorgans as a function of the recombination probability: formula_3  
During meiosis, synapsis (the pairing of homologous chromosomes) ordinarily precedes genetic recombination. 
Homologous chromosomes do not function the same in mitosis as they do in meiosis.
Prior to every single mitotic division a cell undergoes, the chromosomes in the parent cell replicate themselves.
The homologous chromosomes within the cell will not pair up and undergo genetic recombination with each other.
Instead, the replicants, or sister chromatids, will line up along the metaphase plate and then separate in the same way as meiosis II - by being pulled apart at their centromeres by nuclear mitotic spindles.
If any crossing over does occur between sister chromatids during mitosis, it does not produce any recombinants.