Chapter 1: 1.3 Origin of Eukaryotic Genomes

Question 1

Define:

Endosymbiont Theory

Answer 1

An evolutionary theory that suggests several key organelles in eukaryotes were taken inside another cell to function in the host

Question 2

In endosymbiont theory:

It is believed that some ———– were able to ———– others

Answer 2

1. Prokaryotes
2. Phagocytose

Question 3

What does it mean to “phagocytose” others?

Answer 3

To “eat” others

Question 4

How did organelles came to be?

Answer 4

The prokaryotes that were eaten up were able to continue living inside the phagocytic cell

Question 5

List:

Evidence supporting that mitochondria and chloroplast have prokaryotic origins

Answer 5

1. Both proliferate through a process similar to binary fission (seen in prokaryotes)
2. Similar morphologies to bactera
3. Genome/DNA is in the form of a circular plasmid, much like bacteria

Question 6

What is the predecessor to mitochondria?

Answer 6

Aerobic (Oxygen using) proteobacterium

Question 7

What is the predecessor of the chloroplast?

Answer 7

Cyanobacteria - a group of bacteria capable of photosynthesis

Question 8

True or False:

Mitochondria and chloroplast DNA can act independently of the nuclear DNA found in the cell

Answer 8

True

Question 9

Define:

Endosymbionts

Answer 9

Organisms that live within the body or cell of another organism

Question 10

True or False:

Endosymbionts are naturally occurring in modern time

Answer 10

True

Question 11

Can DNA produce their own proteins? Why or why not?

Answer 11

Yes they can, as they have their own DNA

Question 12

True or False:

Mitochondria coding system for protein production is the same as the rest of the cell

Answer 12

False, it is different than the rest of the cell

Question 13

How are mitochondria and their DNA passed on?

Answer 13

Can only be passed on from the mother
* The ovum donates all the cytoplasm to a zygote

Question 14

What mutations can have wide spread effects on the mitochondria and the organism as a whole?

Answer 14

Mutation in mtDNA or the proteins it forms

Question 15

Define:

Petite mutation

Answer 15

An mtDNA mutation that results in super tiny mitochondria in yeast cells

Question 16

In petite mutations:

Cell colonies are ——- for cells that carry this mutation

Answer 16

Smaller

Question 17

In petite mutations:

Why is colony growth stunted?

Answer 17

The mitochondria are not making enough ATP

Question 18

In petite mutations:

What happens if a petite mutation cell and a cell with normal mitochondria exchange genetic material?

Answer 18

Both cells become normal through a process called heteroplasmy

Question 19

True or False:

mtDNA mutations segregrate identically during cell division

Answer 19

False, mtDNA mutations can segregate differently during cell division

Question 20

Can mutations in mtDNA change the lifespan of an organism?

Answer 20

Yes, causing it to live longer or shorter

Question 21

What can result from mtDNA mutations?

Answer 21

Diseases in individual structures such as:
* Nerves
* Muscles
* Organs (diabetes)
* Senses (deafness)

Question 22

Mitochondria are able to —— themselves and —- with other mitochondria

Answer 22

1. Divide
2. Fuse

Question 23

Define:

Mitochondria Fission

Answer 23

The division of a single mitochondrion into two daughter mitochondria

Question 24

Define:

Mitochondria Fusion

Answer 24

The coming together and union of two separate mitochondria to make a single mitochondrion

Question 25

How was fission and fusion proved in mitochondria?

Answer 25

Using yeast and causing mutations in genes that regulate fission and fusion
* Normal yeast had mitochondria that mixed, mutated cells did not

Question 26

Why are mitochondria able to undergo fission and fusion?

Answer 26

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

Question 27

Describe:

Mitochondrial Fission

Answer 27

The mitochondrion is squeezed apart by GTPase enzyme and DRP1

Question 28

Where does mitochondrial fission often occur?

Answer 28

Happens where the mitochondrial associated membrane (MAM) of the ER meets with the mitochondria

Question 29

What is the mitochondrial fusion process split into?

Answer 29

1. The fusion of the outer membrane
2. The fusion of the inner membrane

Question 30

In mitochondrial fusion:

Describe the fusion of the outer membrane

Answer 30

• 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

Question 31

In mitochondrial fusion:

Describe fusion of the inner membrane

Answer 31

• Regulated by OPA1 protein
• OPA1 forces the inner membranes together, causing fusion

Question 32

Why does mitochondrial fission/fusion occur?

Answer 32

1. To spread out reactive oxygen molecules
2. Helps mitochondria segregate equally into daughter cells when the cell divides

Question 33

What are reactive oxygen molecules?

Answer 33

Superoxide pollutants

Question 34

Why are mitochondria prone to having a build up of reactive oxygen molecules?

Answer 34

Mitochondria are in the energy production business

Question 35

True or False:

If a mitochondria has too many pollutants, it can be destructive to the cell

Answer 35

True, it can be destructive to itself AND the cell

Question 36

How can a ‘sick’ mitochondria be healthy again?

Answer 36

Via fusion with a healthy one
* Results in one large healthy mitochondria
* When they divide by fission, they are both healthy again

Question 37

If mitochondrial fission is not happening properly:
1. What caused it?
2. What may result from this?

Answer 37

1. Usually due to a problem with DRP1
2. Daughter cells will not receive equal amounts of mitochondria