Understanding Genetic Mutations: Types, Effects, and Inheritance
Mutation: A type of genetic exchange that will affect a recessive characteristic when the effect of the genetic alteration is not immediately apparent in the individual. In contrast, with a dominant characteristic, the effect of the genetic alteration is manifested in the individual.
Mutations can affect somatic cells and the organism. Note: Mutations that are produced in somatic cells, when the cell multiplies, all the daughter cells will have the mutation and form a clone. These mutations are not transferred to the offspring, only to the cells that arise from the mitotic mutant cell.
Germline mutations: These are mutations that affect germ cells. They are transmitted to the stem cell progeny.
Groups of Mutations
- Gene: Affects only one gene.
- Chromosome: Affects segments of chromosomes, whole chromosomes, or complete sets of chromosomes.
Specific Mutation Types
Albinism: An autosomal recessive disorder characterized by the inability to produce pigment in the skin, eyes, and hair.
Polyploidy: A type of mutation that arises when the gametes undergo meiosis, and in the process of fertilization, humans acquire more than two haploid sets of chromosomes (e.g., 3n triploid, 4n tetraploid). This is common in plants.
Aneuploidy: The loss or appearance of an extra chromosome.
Chromosomal mutations: Changes in the structure or number of chromosomes. These may vary due to errors in cell division, producing polyploidy and aneuploidy.
Gene mutations: These are due to the replacement or loss of a part of the gene, which originates a malfunction. They can happen spontaneously or be induced by mutagenic agents. They can cause morphological changes, such as albinism, which changes the color of the skin, or changes in several metabolic functions. Some are lethal, such as Tay-Sachs disease, which manifests itself during the first few months of life.
Principles of the Chromosomal Theory of Inheritance
Every living being has a set of characteristics that define its form and function through genes, which are encoded in the DNA of their chromosomes. There is a relationship between the characteristics that are inherited and the process of meiosis, which forms gametes that originate the zygote.
Mendel’s Contributions
Successes: Mendel chose a plant whose varieties showed some pure characteristics that did not change generation after generation.
- Used self-pollination to identify a plant. The petals enclose the stamens and pistil, thereby avoiding accidental cross-pollination with different plants, and pure breeds can be obtained.
- Used a plant that was easy to manipulate.
- Applied statistics to the study of inheritance. He counted the varieties of peas obtained from crosses and found a mathematical relationship that allowed him to extract a rule explaining the transmission of characters in inheritance.
Mitosis
- Takes place in somatic cells.
- Two daughter cells are derived from the parent cell.
- Parent cell chromosomes: 2n (diploid).
- Function: body growth, renewal of cells and tissues, maintenance of the individual’s life.
- One cell division.
- No genetic recombination.
- Derived cells: all cell types.
Meiosis
- Takes place in germ cells in reproductive organs.
- Four daughter cells are obtained from each parent cell.
- Parent cell chromosomes: 2n (diploid).
- Daughter cell chromosomes: haploid (n).
- Function: continuity of the species, increased genetic variability.
- Two cell divisions.
- Genetic recombination occurs.
- Cells obtained: gametes.
IVAN Ariza – 4th Year, 2008/2009 (Biology)