What is extranuclear inheritance? Describe three examples. Explain the variegated phenotype in Mirabilis jalapa (four-o- clock plant) in terms of chloroplast present in the cell.
Extranuclear inheritance refers to the transmission of genetic information from non-nuclear genetic material that is not present in the nucleus of cells. The three main types of extranuclear inheritance include mitochondrial inheritance, chloroplast inheritance, and infectious inheritance.
Examples of extranuclear inheritance include:
1. Mitochondrial inheritance: Mutations in mitochondrial DNA are transmitted from the mother to offspring. Mitochondria contain their own DNA, which is separate from the nuclear DNA. Mitochondrial disorders, such as Leigh syndrome, can result from mutations in mitochondrial DNA.
2. Chloroplast inheritance: Similar to mitochondrial inheritance, chloroplasts also contain their own DNA and are only inherited from the mother. Chloroplasts are responsible for photosynthesis in plant cells, and mutations in chloroplast DNA can affect plant growth and development.
3. Infectious inheritance: Some viral and bacterial infections can be inherited from the parent. For example, bacterial endosymbionts can be passed from mother insects to their offspring and can affect various phenotypic traits.
The variegated phenotype in Mirabilis jalapa (four-o-clock plant) can be explained by the presence of chloroplasts in the cells. The chloroplasts contain their own DNA, which can undergo mutations and affect the coloration of the leaves. The variegated phenotype is caused by a mixture of cells with normal chloroplasts and cells with mutated chloroplasts, leading to a mosaic pattern of green and white in the leaves. This type of inheritance is not predictable, as the random distribution of mutated chloroplasts results in different patterns of variegation in each individual plant.