Biology help! Genes and chromosomes linked?

Can someone explain why genes located on one chromosome are said to be linked. Why do linked genes sometimes separate during meiosis?





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Biology help! Genes and chromosomes linked?
To understand the answer to your question, you need to read about the genetic concepts of segregation, independent assortment, and crossing over.





If two genes are located very close to one another on a chromosome, they will assort together. Basically this means that it is very difficult to separate them and they will "tag along" with each other when new cells are created (the only COMMON way for them to be separated is that a crossing over event must happen BETWEEN the respective genes, which is not very likely because they are very closely associated on a chromosome and there usually is not much intervening DNA at which a cross over may occur). The result is that you find that the two genes are almost always inherited together. In the real world, you may find this perhaps as a certain disease occurring in only left-handed individuals (because these two genes, and hence the two traits are inherited together).
Reply:A chromosome is like a very long continuous piece of DNA molecule which contains many genes. During meiosis, chromosomes align in the metaphase plate. They are randomly oriented with either parental homologue on a side. This is where mix and match of genes happens - that leads to 50-50 chance for the daughter cells to get either the mother's or father's homologue for each chromosome.