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Genetic Inheritance

  Chromosomal theory of inheritance Genes are located on chromosomes. Chromosomes are in pairs and genes, or their alleles, are located on each of these pairs. When the cell divides in half, each chromosome ends up in a different cell. This is seen during meiosis in formation of egg cells of sperms. The genes also split into two halves. These are called alleles. Meiotic products have one of each homologous chromosome but not both. Meiosis is a series of cell divisions that creates haploid cells with half of the total number of chromosomes. Once the egg and sperm meet, the pairs are restored but now the genetic combination of the pair is altered. One of the alleles thus comes from the mother and another from the father. This is how a defective gene causing a genetic disorder is also inherited by offspring. Gene Linkage on Chromosomes As per the Mendelian principles of inheritance genes need to be inherited independently of each other. However, there are far more genes than chromosom...
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Neanderthal genes shape human noses

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The genetics of facial features GWAS of human facial characteristics has been used to explain the genetic causes of different facial features among people. Genomic regions equipped with regulatory elements that are active during craniofacial development have been identified, many of which overlap with developmental genes. These findings have been published mainly in studies conducted on people of European origin. More recently, GWASs that focus on facial features have included non-European populations. Non-European characterization is aiding in the comprehensive understanding of the variable genetic composition and evolution of facial characteristics in humans. Example skulls from a modern human (Native American) and a Neanderthal (Amud 1). The 3D images are reproduced on the scale shown underneath. Nasal height (distance between the nasion and sub-spinale landmarks) is shown as a red line (modern human = 50.2 mm; Neanderthal = 63.8 mm). The modern human image is from the collection of...
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