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  • Daniel Ya

FISH: Probing the Mysteries of Our Genes

The chromosome is complicated. Think of it like a super organized, tightly packed spaghetti noodle made of DNA. It's coiled, looped, and folded in ways that would make your head spin. This single spaghetti strand is loaded with genes, the instructions for making you who you are. But there are millions of genes here, all neatly arranged along the length of the chromosome. The chromosome is like a massive bookshelf filled with tiny books with each containing a different story about you. So how exactly do geneticists track down the precise location of genes on a chromosome? The method is surprisingly simple if we break it down.

Geneticists have come up with this method called fluorescence in situ hybridization, abbreviated into the quite comical name FISH. It's like a tracker for genetic material inside your cells. Researchers can use it to understand all sorts of genetic abnormalities and mutations. Here's how it works: First, a researcher prepares single-stranded tiny pieces of DNA called probes. These pieces of DNA match a part of a gene the researcher is looking for through complementary base pairing. If you’ve gone through school before, you should think of how adenine binds to thymine and cytosine binds to guanine. That is the complementary base pairing of nucleotides. These probes get tagged with fluorescent colors of fluorescent dye that glow like glow sticks. But before any action could happen, both the target sequence with the gene and the probe sequences must be denatured with heat or chemicals. This means that the double-stranded DNA must be separated so that complementary bonds can form between the target and the probes when they are mixed together. When the target and probes are allowed to know one another during hybridization, the probes latch onto their complementary buddies on the target gene. They light up, showing the researcher exactly where they've landed. 

A glowing masterpiece of genetic innovation! The red spots indicate where fluorescent probes are on the chromosomes and the locations of the genes.

Now that we’ve explained how FISH works, how can it be useful in real-world medicine? Our genes can make mistakes. During genetic replication, some sections of DNA might miss out on being filled in, resulting in a deletion mutation. Or the wrong nucleotide might take the place of the correct nucleotide, resulting in a point mutation. Our genes are what make us us, and like us, our genes can make mistakes. We are not perfect, but FISH can help us understand our quirks. FISH is super important for finding specific genetic changes in cancer, like extra HER2 genes in breast cancer. FISH is also super handy for diagnosing genetic disorders, like spotting the extra chromosome that causes Down syndrome. It's additionally used to keep an eye on bone marrow transplants by checking the patient's cells for changes. Plus, FISH can help doctors detect chromosomal issues in unborn babies, so parents and doctors can plan ahead and make informed choices early on. 

To conclude, we humans are complicated because of the sheer complexity of the genes that each make us unique. But with FISH, the mysteries of ourselves are getting unraveled, one probe at a time.

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