Genetics is the study of heredity, the process of a parent passing on certain genes to their children. A person`s appearance – height, hair color, skin color and eye color – is determined by genes. Other traits affected by heredity include: Also known as Mendel`s second law of inheritance, the law of independent sorting states that during gamete formation, a pair of traits separates independently from another pair. Since individual inheritance factors interact independently of each other, different traits have the same chances of occurring together. Victoria Genetic Services provides genetic counselling, counselling, screening and diagnosis services to children, adults, families and intended parents. They also provide recommendations to community resources, including support groups, as needed. Humans have cells with 46 chromosomes. These consist of 2 chromosomes that determine the sex they have (X and Y chromosomes) and 22 pairs of non-sex chromosomes (autosomal). Men are „46,XY“ and women are „46,XX“.
Chromosomes are made up of strands of genetic information called DNA. Each chromosome contains segments of DNA called genes. Genes carry the information your body needs to make certain proteins. Select the correct answer and click on the „Finish“ button, check your score and answers at the end of the quiz The combination of alleles you have is called a genotype (e.g. AO). The observable trait you have – in this case, blood type A – is your phenotype. The ancient Babylonians knew that pollen from a male date palm had to be applied to the pistils of a female tree to produce fruit. The German botanist Rudolph Jacob Camerarius showed in 1694 that this also applies to corn.
The Swedish botanist and explorer Carolus Linnaeus in 1760 and the German botanist Josef Gottlieb Kölreuter described crosses of plant varieties and species in a series of works published from 1761 to 1798. They found that, overall, these hybrids were intermediate between parents, although they may be closer to one parent in some traits and closer to the other parent in others. Kölreuter compared the offspring of reciprocal crosses – that is, crosses of variety A that function as females – with variety B as males and vice versa, variety B as female with A as male. The hybrid offspring of these crosses were generally the same, suggesting that, contrary to Aristotle`s belief, the hereditary endowment of the offspring came equally from female and male relatives. Many other experiments on plant hybrids were conducted in the 1800s. These studies also found that hybrids are usually found between parents. By the way, they recorded most of the facts that later led Gregor Mendel (see below) to formulate his famous rules and justify the gene theory. Apparently, none of Mendel`s predecessors saw the importance of data collection. The general intermediality of hybrids seemed to be most consistent with the belief that inheritance from parents to offspring was passed down through „blood,“ and this belief was shared by most 19th century biologists. Charles Darwin, the English naturalist, was accepted in the nineteenth century. Heredity has long been one of nature`s most mysterious and mysterious phenomena. Indeed, the sex cells that form the bridge over which inheritance must pass between generations are generally invisible to the naked eye.
It was only after the invention of the microscope at the beginning of the 17th century and the subsequent discovery of sex cells that the essence of heredity could be grasped. Before this time, the ancient Greek philosopher and scientist Aristotle (4th century BC) hypothesized that the relative contributions of female and male relatives were highly unequal; It was believed that the female provided what he called „matter“ and the male „movement“. The Manu Institutes, which were established in India between 100 and 300 AD. consider the role of the female as that of the field and the male as that of the seed; New bodies are formed „by the combined action of seed and field“. In reality, both parents pass on the inheritance model equally and, on average, children resemble their mother as much as their father. Nevertheless, female and male sex cells can be very different in size and structure; The mass of an egg is sometimes millions of times larger than that of a sperm. In the early 1900s, a number of genetic alterations (mutations) were identified in Drosophila that normally affect easily observable traits such as eye color or wing shape. Selection experiments have shown that some of the genes that control these traits are inherited independently, suggesting that these genes are located on different chromosomes that separate independently during meiosis (Figure 3.3). However, other genes are often inherited as paired traits. Such genes are supposed to be linked together because they are located on the same chromosome.
The number of linked gene groups is the same as the number of chromosomes (four in Drosophila), which supports the idea that chromosomes carry genes.
Komentari su zatvoreni.