Chapter 1: 1.3 Origin of Eukaryotic Genomes Flashcards
Define:
Endosymbiont Theory
An evolutionary theory that suggests several key organelles in eukaryotes were taken inside another cell to function in the host
In endosymbiont theory:
It is believed that some ———– were able to ———– others
- Prokaryotes
- Phagocytose
What does it mean to “phagocytose” others?
To “eat” others
How did organelles came to be?
The prokaryotes that were eaten up were able to continue living inside the phagocytic cell
List:
Evidence supporting that mitochondria and chloroplast have prokaryotic origins
- Both proliferate through a process similar to binary fission (seen in prokaryotes)
- Similar morphologies to bactera
- Genome/DNA is in the form of a circular plasmid, much like bacteria
What is the predecessor to mitochondria?
Aerobic (Oxygen using) proteobacterium
What is the predecessor of the chloroplast?
Cyanobacteria - a group of bacteria capable of photosynthesis
True or False:
Mitochondria and chloroplast DNA can act independently of the nuclear DNA found in the cell
True
Define:
Endosymbionts
Organisms that live within the body or cell of another organism
True or False:
Endosymbionts are naturally occurring in modern time
True
Can DNA produce their own proteins? Why or why not?
Yes they can, as they have their own DNA
True or False:
Mitochondria coding system for protein production is the same as the rest of the cell
False, it is different than the rest of the cell
How are mitochondria and their DNA passed on?
Can only be passed on from the mother
* The ovum donates all the cytoplasm to a zygote
What mutations can have wide spread effects on the mitochondria and the organism as a whole?
Mutation in mtDNA or the proteins it forms
Define:
Petite mutation
An mtDNA mutation that results in super tiny mitochondria in yeast cells
In petite mutations:
Cell colonies are ——- for cells that carry this mutation
Smaller
In petite mutations:
Why is colony growth stunted?
The mitochondria are not making enough ATP
In petite mutations:
What happens if a petite mutation cell and a cell with normal mitochondria exchange genetic material?
Both cells become normal through a process called heteroplasmy
True or False:
mtDNA mutations segregrate identically during cell division
False, mtDNA mutations can segregate differently during cell division
Can mutations in mtDNA change the lifespan of an organism?
Yes, causing it to live longer or shorter
What can result from mtDNA mutations?
Diseases in individual structures such as:
* Nerves
* Muscles
* Organs (diabetes)
* Senses (deafness)
Mitochondria are able to —— themselves and —- with other mitochondria
- Divide
- Fuse
Define:
Mitochondria Fission
The division of a single mitochondrion into two daughter mitochondria
Define:
Mitochondria Fusion
The coming together and union of two separate mitochondria to make a single mitochondrion
How was fission and fusion proved in mitochondria?
Using yeast and causing mutations in genes that regulate fission and fusion
* Normal yeast had mitochondria that mixed, mutated cells did not
Why are mitochondria able to undergo fission and fusion?
Endosymbiont Theory: The idea that mitochondria were once their own cell
* Engulfed by a eukaryotic cell and lived inside in a symbiotic relationship with the engulfing cell
* If mitochondria were their own cell, they would need a way to divide and replicate themselves
Describe:
Mitochondrial Fission
The mitochondrion is squeezed apart by GTPase enzyme and DRP1
Where does mitochondrial fission often occur?
Happens where the mitochondrial associated membrane (MAM) of the ER meets with the mitochondria
What is the mitochondrial fusion process split into?
- The fusion of the outer membrane
- The fusion of the inner membrane
In mitochondrial fusion:
Describe the fusion of the outer membrane
- Regulated by mitofusion proteins called MSFN1 and MSFN2
- MSFN1 and 2 become a dimer and force the cells together, rupturing the other membrane
- Once its ruptured, fusion can begin
In mitochondrial fusion:
Describe fusion of the inner membrane
- Regulated by OPA1 protein
- OPA1 forces the inner membranes together, causing fusion
Why does mitochondrial fission/fusion occur?
- To spread out reactive oxygen molecules
- Helps mitochondria segregate equally into daughter cells when the cell divides
What are reactive oxygen molecules?
Superoxide pollutants
Why are mitochondria prone to having a build up of reactive oxygen molecules?
Mitochondria are in the energy production business
True or False:
If a mitochondria has too many pollutants, it can be destructive to the cell
True, it can be destructive to itself AND the cell
How can a ‘sick’ mitochondria be healthy again?
Via fusion with a healthy one
* Results in one large healthy mitochondria
* When they divide by fission, they are both healthy again
If mitochondrial fission is not happening properly:
1. What caused it?
2. What may result from this?
- Usually due to a problem with DRP1
- Daughter cells will not receive equal amounts of mitochondria
