Have you ever wondered how traits and characteristics are passed down from generation to generation? This happens through a phenomenon called genetic inheritance. There are two main inheritance patterns. They are the chromosomal inheritance and extrachromosomal inheritance.
What is the difference between chromosomal and extrachromosomal inheritance? In chromosomal inheritance, genes present on the chromosomes pass from parent to offspring. In extra-chromosomal inheritance, genes found in cytoplasmic organelles, especially in mitochondria and chloroplasts, pass from one generation to another. Chromosomal inheritance follows the Mendelian inheritance pattern, whereas extra-chromosomal inheritance follows a non-Mendelian inheritance pattern.
CONTENTS
1. Overview and Key Difference
2. What is Chromosomal Inheritance
3. What is Extrachromosomal Inheritance
4. Similarities – Chromosomal and Extrachromosomal Inheritance
5. Chromosomal vs. Extrachromosomal Inheritance in Tabular Form
6. Summary – Chromosomal vs. Extrachromosomal Inheritance
7. FAQ – Chromosomal and Extrachromosomal Inheritance
What is Chromosomal Inheritance?
Chromosomal inheritance is a type of inheritance where the genes (the units of heredity) found in the chromosomes are passed from parent to offspring. The chromosomal theory of inheritance was first explained by Boveri and Sutton in the 1900s. In chromosomal inheritance, genes are inherited according to Mendel’s law. In other words, chromosomes are the responsible genetic materials for the Mendelian inheritance. Chromosomal inheritance is one of the fundamental concepts in genetics.
Figure 01: Chromosomal Inheritance
Genetic diseases arise from errors in chromosomal inheritance. Examples include Down syndrome and Huntington’s disease, both stemming from issues in chromosomal transmission. Down syndrome occurs when there is an extra copy of chromosome 21, leading to mental deterioration. Huntington’s disease occurs due to a mutation in chromosome 4, leading to the progressive degradation of nerve cells in the brain.
What is Extrachromosomal Inheritance?
Extra-chromosomal inheritance is the vertical transmission of hereditary characters by DNA from cytoplasmic organelles like mitochondria, chloroplasts, and plastids or from plasmids or viral episomal DNA. This concept was first introduced by Boris Ephrussi in 1949. It is also known as extranuclear inheritance or cytoplasmic inheritance.
Figure 02: Extrachromosomal Inheritance
In extrachromosomal inheritance, the traits do not follow the conventional pattern of Mendelian inheritance pattern. Furthermore, in this type of inheritance, extrachromosomal hereditary factors have the ability to self-replicate and transmit sexually or asexually. Examples of extrachromosomal inheritance are plastid inheritance in MIrabilis jalapa, cytoplasmic male sterility in maize, kappa particles in paramecium, and sigma particles in the fruit fly, Drosophila.
Similarities Between Chromosomal and Extrachromosomal Inheritance
- Chromosomal inheritance and extrachromosomal inheritance are two different types of inheritance in organisms.
- Both types are able to pass DNA to offspring.
- These types immensely contribute to variations.
- Both types are important for the survival and sustenance of the organisms.
Comparing the Difference Between Chromosomal and Extrachromosomal Inheritance
Inheritance from Parent to Offspring
- In chromosomal inheritance, genes in the chromosomes are passed from parent to offspring.
- In extra-chromosomal inheritance, non-nuclear DNA, especially genes in cytoplasmic organelles, are passed from parent to offspring.
Mendelian Inheritance
- Chromosomal inheritance follows the Mendelian pattern of inheritance.
- Extrachromosomal inheritance does not follow the Mendelian pattern of inheritance.
Amount of Genetic Material Transmitted
- In chromosomal inheritance, large amounts of genetic material are transmitted.
- In extrachromosomal inheritance, small amounts of genetic material are transmitted.
Examples of Chromosomal and Extrachromosomal Inheritance
- Down syndrome and Huntington disease are examples of chromosomal inheritance.
- Plastid inheritance in MIrabilis jalapa, cytoplasmic male sterility in maize, and kappa particles in paramecium are examples of extrachromosomal inheritance.
The following table summarizes the difference between chromosomal inheritance and extrachromosomal inheritance.
Summary – Chromosomal vs. Extrachromosomal Inheritance
Chromosomal inheritance and extrachromosomal inheritance are two different types of inheritance by which genetic material passes from one generation to another. Chromosomal inheritance is a type of inheritance where nuclear DNA, especially genes located on the chromosomes, are passed to the offspring. On the other hand, extrachromosomal inheritance is a type of inheritance where non-nuclear DNA or DNA found in cytoplasmic organelles like mitochondria is passed to the offspring. Thus, this is the key difference between chromosomal inheritance and extrachromosomal inheritance.
FAQ: Chromosomal and Extrachromosomal Inheritance
1. What is the difference between chromosomal and extrachromosomal DNA?
- Chromosomal DNA is found on the chromosomes present inside the nucleus while extrachromosomal DNA is found in cytoplasmic organellesand in the cytoplasm. This is the main difference between chromosomal and extrachromosomal DNA.
2. What is the role of mitochondria in extrachromosomal inheritance?
- In extrachromosomal inheritance, genetic information stored in the mitochondrial DNA is passed from mother to offspring. But this type of inheritance does not follow the Mendelian inheritance.
3. What is an example of chromosomal inheritance?
- An example of chromosomal inheritance is Duchenne muscular dystrophy (DMD). This genetic disorder is caused by mutations in the dystrophin gene located on the X chromosome. Since males have only one X chromosome, they are more severely affected by this disorder compared to females, who have two X chromosomes and can often be carriers without displaying symptoms.
4. How is extrachromosomal DNA replicated?
- Chromosomal disorders are typically inherited through errors in chromosome segregation during meiosis. This leads to an abnormal number or structure of chromosomes in the offspring. Chromosomal disorders can also arise from spontaneous mutations or environmental factors affecting chromosome structure or number.
5. What is the role of extrachromosomal DNA?
- The role of extrachromosomal DNA, such as mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA), is to encode essential genes necessary for the functions and replication of these organelles. Additionally, extrachromosomal DNA plays a vital role in cellular energy production, as mitochondria are responsible for generating ATP through oxidative phosphorylation.
Reference:
1. “13.1A: Chromosomal Theory of Inheritance.” Biology LibreTexts, Libretexts.
2. “Extranuclear Inheritance.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “1.4. The inheritance of chromosomes” (CC BY-NC-ND 2.0 DEED) via Flickr
2. “Image from page 135 of “The cell in development and inheritance” (1896)” By Biosciences For Farming in Africa (CC BY-NC-ND 2.0 DEED) via Flickr
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