Mendelian Genetics: Laws, Inheritance, and Applications
Gregor Mendel and the Foundations of Genetics
Gregor Mendel (1822-1884)‘s experiments on plant breeding were central to the development of genetics. He meticulously planned his experiments by choosing plants with contrasting characters.
Materials Used in Mendel’s Experiments
Materials used: Green and yellow seeds, seeds with smooth and rough surfaces. These materials provided the contrasting characters necessary for his research.
Mendel recognized that inheritance follows specific laws and that the characteristics of offspring could be predicted with a high degree of accuracy.
Mendel’s Success and the Laws of Inheritance
Mendel’s success led to the creation of Mendel’s Laws, which form the foundation of genetics. Although his work remained forgotten for a time, it highlighted the role of certain factors (later discovered to be genes) in the inheritance of characteristics.
Rediscovering Mendel’s Work
The scientists who rediscovered Mendel’s work include Tschermak in Austria, Correns in Germany, and De Vries in the Netherlands.
Mendelian Inheritance: Mendel’s Laws
1st Law: Law of Segregation of Characters
When crossing two varieties that differ in one character, the first generation hybrids exhibit only the dominant character of the parents. In the second generation, the recessive character reappears.
2nd Law: Law of Independent Transmission of Characters
When crossing two varieties of plants or animals that differ in two characters, each character is transmitted independently of one another.
Key Concepts in Genetics
Genetics
The branch of biology that studies all aspects relating to inheritance and variation.
Inheritance
The process by which biological characteristics are passed down from parents to offspring.
Dominant Character
A trait that is manifested in the phenotype of the offspring, even with only a single gene for that character.
Recessive Character
A trait that manifests itself in the phenotype of descendants only when two genes for that character are present.
Gene
The factor that controls a hereditary characteristic.
Homozygous Genes
Pure-bred individuals have a pair of identical genes for a particular character.
Heterozygous Genes
Hybrid individuals have pairs of genes with different alleles.
Types of Crosses
Monohybrid Cross
A cross where there is one contrasting feature.
Dihybrid Cross
A cross where there are two contrasting characteristics.
Incomplete Dominance
Refers to the action of genes that is more complex than initially assumed. Dominant and recessive characters are not always as clear as in the pea plant; some characters can be mixed. For example: a cross between a plant with red flowers and a white flower leads to the 1st generation plants exhibiting pink flowers. When these self-pollinate, the characters begin to split, and the original red and white colors reappear.
Applications of Genetics
The applications of genetics include:
- Biotechnology: Involves the manipulation of genes.
- Human Genome: Seeks to uncover the function of each gene and produce a map to determine the location of genes on chromosomes.
Research centers for genetics in Venezuela include:
- Central University (UCV)
- School of Biology, Veterinary Medicine, Agronomy, Medicine, etc.
- Universidad de Oriente (UDO)
- University of Zulia (LUZ)
- Universidad de Los Andes (ULA)
- Experimental College of the Plains Ezequiel Zamora
- Venezuelan Institute of Scientific Research (IVIC)
- National Agricultural Research Fund (FONAIAP)
Cloning
Cloning: Obtaining an organism through asexual reproduction from another organism, resulting in a true copy. The resulting product is a genetically identical organism to the one that gave rise to it.
Example of Cloning
An example of cloning is the nuclear transfer technique, which involves removing a mammary cell from a sheep (donor). This cell is inserted into a host egg from which the nucleus has been removed. Using an electric shock, the mammary cell nucleus enters the egg. The zygote thus formed begins to divide and reaches the embryo stage, called the blastocyst stage. The embryo is then implanted in the uterus of an adult sheep to complete gestation (150 days). After pregnancy, a lamb is born with gene characteristics identical to those of the donor sheep.