The study of genes is an important part of biology. It can be used to\ndiagnose diseases and understand how they develop. It can also help scientists\ndevelop drugs that treat genetic disorders.<\/p>\n\n\n\n
Modern genetics began in the mid-1800s when Gregor Mendel studied traits\nin pea plants. He discovered patterns of inheritance that are now known as\nMendel\u2019s Laws.<\/p>\n\n\n\n
Polymerase chain reaction<\/strong><\/p>\n\n\n\n The polymerase chain reaction (PCR) is a laboratory technique that\nenables scientists to quickly produce billions of copies of a specific segment\nof DNA. This technique allows scientists to examine the structure and function\nof genes in greater detail than would be possible with other methods. It is a\nfundamental tool in molecular biology research and is used in many different\ntypes of genetic investigations.<\/p>\n\n\n\n Genes are like master instructions that tell cells how to make proteins,\nthe building blocks of our bodies. To keep the genes safe, the cell makes small\ncopies of them in a molecule called RNA. These copies act as templates for\nmaking proteins, much the way an IKEA instruction manual might be used to build\na cabinet. PCR can detect these RNA molecules and determine which genes are\nbeing expressed in the sample. PCR is a key technique for studying gene\nexpression, and it is also used to study the relationship between genes and\ncommon diseases such as cancer.<\/p>\n\n\n\n Scientists can use PCR to find out which genes are responsible for\ncertain conditions, such as heart defects or rare forms of blood cancer. They\ncan also use it to investigate how genes work under different circumstances,\nsuch as temperature or other environmental factors. They can even use it to\namplify fragments of DNA found in preserved tissues, such as those from a\n40,000-year-old woolly mammoth or a 7,500-year-old human found in a peat bog.<\/p>\n\n\n\n The most comprehensive genetic tests look at all of a person\u2019s genes and\ncan be used to diagnose complex diseases. These tests include a single gene,\nexome, and whole genome sequencing. They are typically ordered by doctors when\nother single gene and panel tests have not provided a diagnosis. These\nlarge-scale tests can often yield findings that are not related to the reason\nthey were ordered, known as secondary findings.<\/p>\n\n\n\n Another method used to study gene expression is serial analysis of gene\nexpression (SAGE). This method involves isolating mRNA from a biological sample\nand then using a cutting enzyme to slice the mRNA into shorter segments. Each\nof these shorter segments has a unique tag sequence at the end, which can be\nused to identify the gene that they came from. The researchers then keep track\nof the amount of mRNA that was produced for each gene and use this information\nto estimate gene expression levels.<\/p>\n\n\n\n Karyotyping<\/strong><\/p>\n\n\n\n Genetic information is stored in chromosomes, which are the building\nblocks of cells. Karyotyping is a method that combines light microscopy and\nchromosome-specific stains to examine the structure of these chromosomes. It is\noften used to detect chromosomal abnormalities that cause diseases and\ndisorders. In humans, a normal karyotype has 46 chromosomes arranged in pairs.\nThe two chromosomes that specify sex (X and Y) are positioned first, followed\nby the other chromosomes. The chromosomes are stained to reveal their length,\nbanding pattern, and position of the centromere. The resulting picture of the\nchromosomes is called a karyogram.<\/p>\n\n\n\n In a karyotype, the chromosomes are usually color-coded to distinguish\nthem from one another. Different staining techniques, such as Giemsa staining\nand R-banding, highlight specific chromosomal features. For example, Giemsa\nstains identify densely packed, gene-poor regions rich in A-T bases. R-banding\nhighlights chromosomal regions rich in G-C bases. A more modern technique,\nspectral karyotyping, assigns each chromosome a unique spectral color by\nhybridizing it with multiple chromosome-specific probes that are labeled with\nfluorescent tags.<\/p>\n\n\n\n Another way to study genes is to measure their activity or expression.\nWhen a gene is active, it produces a molecule called messenger ribonucleic\nacid, or mRNA. This molecule contains the instructions needed to make proteins.\nmRNA can be detected by a type of laboratory test known as a Northern blot. By\ntracking the amount of mRNA produced by a gene, researchers can determine\nwhether the gene is overactive or underactive.<\/p>\n\n\n\n Genes can also be studied by studying the protein they produce. To do\nthis, a small copy of the gene is made and compared to a printout of the large\ndatabase of instructions that makes up DNA. If the mRNA copy is missing or\nmisplaced, it will no longer function properly, just like a piece of furniture\nwithout an instruction manual.<\/p>\n\n\n\n