Earth Science: Genetics Human- Hereditary rules
Classic genetics is the study of hereditary laws of individuals passing genes to their descendants. The first geneticist was a monk called Johann Gregor Mendel, who formulated the first genetic laws during the 19th century.
Initially, Mendel carried out his experiments using homozygous pea plants, which only differed in a few traits (for example, flower color). He crossed different varieties using artificial pollination, then carried out statistical analyses of his observations.
His results showed regularities from which he deducted three laws, now known as Mendel’s rules or Mendel’s laws.
Inheritance of a trait
If two homozygous individuals of one species differing in one trait, for example, red and white flowers, are crossed, then the first generation (first filial generation F1) will produce offspring with the same expression of the trait (uniform). Therefore, Mendel’s experiments only resulted in peas with red flowers.
Alternating the parental sex during crossbreeding gave the same results with an even distribution of colors throughout the filial generation (reciprocity); for example, white female flowers and red male flowers, or vice versa. Mendel’s first law is also referred to as the law of segregation, reflecting the concept of equal segregation.
However, the second allele (white flowers) has not been lost but is passed on within the genotype of the F1 generation. The trait for flower color is present in the form of two alleles and the phenotype is determined by the dominant one. This is easy to prove by cross-breeding heterozygous individuals of the F1 generation.
Their descendants (F2 generation) do not look alike, but their expressed characteristics differ with a ratio of 3:1 (dominant- recessive cross) or 1 :2:1 (intermediate cross). Mendel’s second law is also called the law of independent assortment.
Inheritance of multiple traits
If individuals differing in multiple traits (genes) are crossed, then each individual gene is passed on independently and recombines during gamete formation (the law of segregation and law of independent assortment both apply to each individual gene).
How- ever, gene pairs need to be located either on different chromosomes or far enough apart to allow free recombination. Mendel’s third law, the law of dominance, is based on this concept.
GENETIC CONTROL ORGANISMS
The fruit fly Drosophila melanogaster an ideal species to study genetics. Gene mutations are easy to recognize n this species, because they manifest, or example, in a change in eye color or wing shape.
Their genome also consists of only eight chromosomes which are extremely large and accessible in the salivary glands. Therefore, the genetic material is very easy to read.
DISCOVERY OF HEREDITARY RULES
During his lifetime, the work of Austrian monk Johann Gregor Mendel (1822-1884) was largely ignored by the entire scientific community. Later, researchers made similar discoveries and his conclusions became the basis of an entirely new branch in sciences.
Amazingly, it took Mendel only about 12 years to complete his revolutionary experiment. Afterward, his monastery appointed him as abbot: a position that required all of his energy and time