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Homologous chromosomes are a pair of which contain a paternal and maternal copy. These copies have the same in the same location, or, as one another. This allows them to pair correctly with one another before separating in or  (U.S. National Library of Medicine, 2013). The homologous chromosomes are randomly segregated, experience, pair up, and separate into two different daughter cells (Pollard, Earnshaw 2008). This is the basis for Gregor Mendel’s laws of genetics.

Overview

 * See also 

Homologous chromosomes are made up of pairs of approximately the same length,  position, and staining pattern, with  for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism's mother; the other from the organism's father. After occurs the daughter cells will have the correct number of genes that are most likely a mix of the two parents' genes. In diploid (2n) organisms, the genome is composed of pairs of homologous chromosomes with one coming from the father and the other from the mother. The on the homologous chromosomes may be different while the genes are the same. This trait is do to crossing over during (Reese et al 2002)

History and the discovery of Homologous Chromosomes
Early in the 1900’s and  were studying inheritance and they noted that some combinations of  appeared more frequently than others. That data and information was further explored by Thomas Morgan. He discovered using es, which focus and reveal the s of a single parent that genes near to one another move together. Using that logic he concluded that the two genes he was studying were both located on homologous chromosomes. Later on during the 1930’s and  were studying  and discovered that the new  combinations present in the offspring and the event of crossing over were directly correlated with each other. (Griffiths et al. 2000).

Structure of Homologous Chromosomes
Homologous chromosomes are chromosomes that have the same order of at the same location. The rest of their structure is identical to that of a regular chromosome.

Homologous Chromosomes in Humans
have 46, which make up 23 pairs of homologous chromosomes. They contain the same but code for different traits in their allelic forms due to the fact that one was inherited from the mother and one from the father (Lodish et al. 2013). So humans have two homologous chromosome sets in each of our cells, meaning we are organisms (Griffiths et al. 2000).

Functions of Homologous Chromosomes
Homologous chromosomes are very important in the processes of and. They allow for the recombination and random segregation of genetic material from the mother and father into new cells (Gregory, The Biology Web). Homologous chromosomes are different from in that sister chromatids are identical, duplicates of each other that are made during  (Pollard, Earnshaw 2008).

Homologous Chromosomes in Meiosis
reduces the number by half by separating the homologous chromosomes in a. In, the homologous chromosomes pair up with one another. The process of meiosis I is generally longer than in meiosis II because time elapses during it for homologous chromosomes to be properly oriented and segregated through the processes of pairing,, and recombination (Pollard, Earnshaw 2008). The implications of by random segregation and crossing over between  are that the daughter cells all contain different combinations of maternally and paternally coded. This creates which helps make a population more stable by providing genetic traits for  to act on.

Prophase I
In prophase I of meiosis I, each becomes aligned with its homologous partner and will pair completely. This occurs by a synapsis process where the - a protein scaffold - is assembled and joins the  along their lengths (Pollard, Earnshaw 2008). Cohesion crosslinking occurs between the homologous chromosomes and helps them resist being pulled apart until anaphase, when they are cleaved by the enzyme to release the homologous chromosome arms from each other (Lodish et al. 2013). The disassembles before anaphase which also allows homologous chromosomes to separate (while the  stay associated) (Pollard, Earnshaw 2008). Genetic crossing over occurs during in prophase of meiosis I. In this process, genes are exchanged by the breakage and union of a portion of the chromosomes’ lengths (Pollard, Earnshaw 2008). Structures called chiasmata are the site of the exchange. They physically link the homologous chromosomes once crossing over occurs and throughout the process of chromosomal segregation during (Pollard, Earnshaw 2008). This allows for the introduction of new gene pairings and.

and proved this intrachromosomal  by examining gene loci on corn  (Griffiths et al. 2000).

Metaphase I
In metaphase I of meiosis I, the pairs of homologous chromosomes, also known as bivalents, line up randomly along the metaphase plate. The random orientation is another way for cells to introduce. Meiotic spindles emanating from opposite spindle poles attach to each homologs (each pair of ) at the (Lodish et al. 2013)  (“Meiosis”, 2013).

Anaphase I
In anaphase I of meiosis I the homologs are pulled apart, which releases the cohesion that held the chromosome arms together, thus allowing the chiasmata to release and the homologs to move to opposite poles of the cell (Lodish et al. 2013). The homologous chromosomes have now been randomly segregated into two daughter cells that will then undergo meiosis II to create four haploid daughter.

==== Problems with Homologous Chromosomes in Meiosis ==== There are severe repercussions when do not segregate properly. It can lead to fertility problems, embryo death}}, [[Congenital disorder|birth defects, and (Gerton, Hawley 2005). Proper homologous chromosome separation in meiosis I is crucial for  separation in meiosis II. Though the mechanisms for pairing and adhering homologous chromosomes vary among organisms, proper functioning of those mechanisms is imperative in order for the final genetic material to be sorted correctly (Gerton, Hawley 2005).

Homologous Chromosomes in Mitosis
Homologous chromosomes function similarly in as in, but there are some differences. Prior to the start of, the in the cell replicate itself so that each [cell division|daughter cell]] will have just as many  as the parental cell. These represent the homologous chromosomes in, which will then separate in the same way as meiosis I (“The Cell Cycle and Mitosis Tutorial, 2004).

Other Uses of Homologous Chromosomes
While the main function of homologous chromosomes is their use in [Mitosis|nuclear division]], they are also used in repairing double-strand breaks of (Sargent et al., 1996). These double-stranded breaks typically occur in that serve as template strands for, and they are the result of , replication errors, or any type of malfunctioning DNA (Kuzminov, 2001). Homologous chromosomes can repair this damage by aligning themselves with chromosomes of the same sequence (Sargent et al., 1996). Once they are oriented correctly, the homologous chromosomes perform a process that is very similar to recombination, or crossing over, as seen in. Part of the intact sequence overlaps with that of the damaged chromosome. Replication proteinsand complexes are then recruited, allowing replication to occur correctly (Kuzminov, 2001). Through this functioning, double-strand breakscan be repaired and can function normally.