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Cytoplasmic & Mitochondrial Inheritance: Types & Impacts

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  • 0:00 Extranuclear Inheritance
  • 1:20 Vegetative Segregation
  • 2:15 Uniparental Inheritance
  • 4:24 Biparental Inheritance
  • 5:09 Lesson Summary
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Lesson Transcript
Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

Everyone knows that you inherit genetic information from your parents, but did you know there are multiple ways for this to occur? In this lesson, we'll look at extranuclear inheritance and see what this means for passing on DNA.

Extranuclear Inheritance

Inheritance is a tricky subject. Sometimes you inherit things you want. Your uncle's million-dollar fortune. Family heirlooms. Sometimes you inherit things you don't want, but you kind of have to take because otherwise you'll hurt someone's feelings. That weird bird clock from your grandma's house. Your great-aunt's entire bottle cap collection. How you inherit genetic traits can be just as tricky. Maybe you got your mom's eyes, or your dad's height, but also a family predisposition to high cholesterol. Yeah, bet you wish you could re-gift that one.

Now, the majority of genetic traits are inherited from both parents and contained on the chromosomes within the cell nucleus. That's where most genetic traits are contained. But, there actually is another way for traits to be passed on. Extranuclear inheritance, sometimes called cytoplasmic inheritance, occurs when genetic traits are inherited from a source outside of the cell nucleus. Extranuclear. Outside the nucleus. See how that works? Organelles like the mitochondria or chloroplasts actually contain genetic information, which is how this can happen. Yep, turns out there are even more ways to inherit things from your family. Lucky you.

Vegetative Segregation

Extranuclear inheritance occurs when genetic information from mitochondria or chloroplast organelles is passed from parent to offspring. There are a few ways this can happen. First we've got vegetative segregation. This is a result of random replication of extranuclear organelles. Basically, during mitotic cellular division, the mitochondria or chloroplasts are randomly replicated and partitioned, and the offspring cell receives a random sampling of the parent's organelles.

This means that additional genetic information may be pumped into the new cell. Considering that extranuclear DNA is much more likely to randomly mutate than DNA within the nucleus, this is significant. We see this a lot in single-celled organisms that reproduced asexually, but also in other cells that divide through mitosis.

Uniparental Inheritance

That's how extranuclear information is passed from parent to child cell. But what about parent to child organisms? The most common ways that extranuclear inheritance occurs in full organisms is called uniparental inheritance, or inheritance of extranuclear genetic information from only one parent. In creatures that reproduce sexually, how is this possible?

Well, the female gamete, the egg cell, is a complex cell that has organisms like mitochondria within it. male gametes, called sperm cells do, too; however during fertilization, the mitochondria within the sperm cells are destroyed, and only the DNA in the nucleus makes it into the egg. So, the fertilized egg contains genetic information from the nucleus of both egg and sperm, but only mitochondrial DNA from the egg. This means some genetic information in the egg mitochondria can only come from the mother and never the father. It can only come from one parent, so it's uniparental. Got it?

The inheritance of genetic information from the mitochondria in the egg is called mitochondrial inheritance. Mitochondrial inheritance transmits genetic information from a mother to children, which means that there are some traits that can only be passed through the mother, not the father. This is especially important with many genetic diseases and conditions.

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