Lec 2.2. Mitochondrial Genetics

Question 1

Mitochondria and chloroplasts contain what?

Answer 1

DNA

Question 2

Mitochondria is the source of what for the cell?

Answer 2

Energy

Question 3

What does Organelle DNA encode for?

Answer 3

Some polypeptides used by the organelle, rRNA and some tRNAs

Question 4

What is the Endosymbiotic theory of origin of organelles (mitochondria and chloroplasts)?*

Answer 4

That mitochondria and chloroplasts were once free-living bacteria

Question 5

What is some supporting evidence to this theory?*

Answer 5

Both organelles are similar to eubacteria, and their DNA sequences within them.

Question 6

What are two unique characteristics from organelle DNA?

Answer 6

Uniparental inheritance of organelle-encoded traits (mostly from mom), replicative segregation.

Question 7

What does heteroplasmic mean?*

Answer 7

Means that not all mitochondria is the same, dif genetic sequence in mitochondria

Question 8

Organelles in a heteroplasmic cell segregate how?

Answer 8

Randomly into the progeny cells.

Question 9

Petite mutations in yeast helped us in what?

Answer 9

Understand mitochondria DNA

Question 10

What are petite mutations in yeast?

Answer 10

Mutations in mtDNA rendering the cells unable to grow on nonfermentable carbon sources.

Question 11

Mitochondrial genomes are generally

Answer 11

small and vary greatly

Question 12

Why do most mitochondrial genes migrate to the nucleus?

Answer 12

Mitochondria cant protect DNA by itself, prone to mutation. Moves to make use of the nucleus repair mechanisms

Question 13

What can cause looping/pairing in plant mitochondria?

Answer 13

Direct repeats. Which result in variation in DNA size

Question 14

Why does mtDNA have a high mutation rate?

Answer 14

Cant repair itself

Question 15

Most copies of mtDNA are

Answer 15

identical

Question 16

What is the reason for some muscle myopathy?

Answer 16

Faulty mitochondria, resulting in low energy production.

Question 17

When do most human diseases associated with damaged mtDNA appear?

Answer 17

Middle age or later

Question 18

Those with mutations in mtDNA start life with decreased or increased oxidative phosphorylation capacity?

Answer 18

Decreased

Question 19

When do heteroplasmic mutations reach threshold to cause changes?

Answer 19

There is no clear threshold, however once that threshold is reached, you get that certain phenotype.

Question 20

What is Leigh syndrome?

Answer 20

Rare genetic neurometabolic disorder that results from mutations causing loss of function of the mitochondria. They reached the threshold, but their mother didnt

Question 21

What are symptoms to Leigh syndrome?

Answer 21

Appear 3months to 2 years of age. Live to teens.

Question 22

How could one prevent transmission of mitochondrial DNA disease?

Answer 22

Pronuclear transfer in human embryos.

Question 23

How does pronuclear transfer work?

Answer 23

Get two eggs, one from mother and donor. Each fertilized with father sperm. Remove the nuclei from the donor egg. Place the nuclei from the mother into the donor egg. Resulting in a child from 3 parents.

Question 24

Does the child from pronuclear transfer usually have any mutated mitochondria after?

Answer 24

Only a little, because some of the mothers cytoplasm got carried over to the donor egg.