Most humans (and vertebrates, in general) are genetically "programmed" to produce a brown skin pigment known as melanin. Albinism--the inability to produce melanin—is inherited in humans as an autosomal recessive trait. An individual with genotype AA or Aa will have normally pigmented skin, whereas an individual with genotype aa will produce no melanin. The albino's skin is very pale white, and the (highly vascularized) irises of the eyes appear red because no melanin obscures the red reflectance of blood.
The frequencies aa (Parental genotype male) and Aa (Parental genotype female, predict the frequencies of all genotypes and phenotypes expected to result from the cross of an albino male with a heterozygous female.
During the past 100 years, the major causes of death have shifted from INFECTIOUS DISEASES to CHRONIC DISEASES.
About a century ago, most diseases were usually acquired by people as a result of infection, that is, the causative organisms are usually passed from one person to another. But since the advent of microbiology in medicine, the trend has change, because the microbes can now be countered using different antibiotic means.
The poreosity dertimes how fast it erodes
Earthquakes can cause very large and catastrophic fires by severing fuel and electricity lines. The released fuel can be lit on fire by something like a cigarette or the severed electrical lines.
