Fundamental Concepts in Genetics and Biology
Mendel’s Laws
- All individuals descended from the cross of two pure races are equal.
- To cross each other, the character of hybrids present in these are separated and are combined at random in the descendants.
- The various characters are inherited independently of one another and are combined at random in the offspring.
Cloning
Cloning, in scientific language, describes the obtaining of an individual identical to another. We call it a clone, i.e., with the same genome. Plants and animals, such as the sponge, maintain totipotent stem cells throughout their adult life, equivalent to embryonic cells.
Central Dogma
- Replication: Only when the cell is to reproduce and copy itself.
- Transcription: When DNA is copied into fragments.
- Translation: When the cytoplasm produces a protein.
Brain Death
Irreversible unconsciousness and loss of the ability to breathe. The evidence of death is brain-cerebral, evidence that the brain has stopped working permanently.
Preimplantation Genetic Diagnosis
- Recover between 10 and 16 ovules from the mother.
- Each egg is injected with a sperm.
- Zygotes are subdivided and become pre-embryos.
- Two are drawn using a biopsy, diagnosed, and classified as genetically normal or not normal.
Basic Genetic Concepts
Genetics: The science of biological inheritance, i.e., the transmission of characters over generations.
Gene: A fragment of nucleic acid (usually DNA and RNA in some viruses) that contains information necessary for a character. (It is the structural and functional unit of hereditary material and corresponds to Mendel’s hereditary factors).
Alleles: Each of the possible ways a gene can be; they are derived by mutation from the original gene. (There are, in general terms, several allelic forms of each gene. The most abundant allele is usually the wild gene. Mutation varies the information encoded by the gene, causing an alteration, often disadvantageous, in the phenotype of the individual).
Example:
- Gene (character) = peel color
- Alleles: N = black, n = white
Genotype: The set of genes of an organism.
Phenotype: The aspect of an organism. It is due to the influence of the environment on the genotype.
Haploid: The cell or organism that has only one chromosome of each type. It is represented by n.
Diploid: The cell or organism with two chromosomes of each type (homologous chromosomes). It is represented by 2n.
Gametes: Reproductive cells are eggs and sperm. They represent the only haploid cells of diploid organisms since they are formed by meiosis.
Homozygote or Purebred: Diploid organisms that have the same two alleles of the same character. In dominant inheritance, there is a homozygous dominant and a recessive.
Heterozygote or Hybrid: A diploid organism that has two different alleles of the same character.
Dominant Inheritance: Characters are those regulated by two alleles of which one, called dominant, is stronger and consequently is always manifested in the heterozygote. Three different genotypes correspond to only two phenotypes because the heterozygote has the same phenotype as the homozygous dominant.
Intermediate Inheritance: One in which the two genes have the same force. In this case, the three genotypes correspond to three distinct phenotypes.