W1: Mitochondrial Genetics

Question 1

Mitochondrial gene is circular/linear, single/double stranded DNA.

Answer 1

Circular, double

Question 2

Mitochondrial genome encodes ___ genes.

Answer 2

37 (polypepetide for respiratory complexes, mt tRNA, mt rRNA)

Question 3

Majority of the respiratory complexes are encoded by mitochondrial/nuclear genes.

Answer 3

nuclear

Question 4

Mitochondrial uses slightly different genetic code from the universal codons. How many are different?

Answer 4

4

Question 5

Which cell type carries the most number of mitochondria?

Answer 5

oocytes

Question 6

What is heteroplasmy in mitochondrial DNA?

Answer 6

Existence of various types of mitochondria in body, tissue, or cell (polymorphism inherited from mother’s maternal ancestors)

Question 7

What is the difference between mitochondrial disorder due to mutation in mtDNA and nuclear DNA?

Answer 7

Heteroplasmy only occurs in mtDNA.

Both mother and father transmit nuclear DNA, whereas mtDNA can only be transmitted maternally.

Question 8

How is genetic testing for mtDNA and nuclear DNA mutations different?

Answer 8

Nuclear DNA - blood test (affect all body)

mtDNA - biopsy of specific tissue (blood test could be misleading)

Question 9

Why are mtDNA unusually mutable?

Answer 9

• no protection from histone
• no DNA repair enzyme
• constant exposure to free radicals

Question 10

What tissues are impacted mostly by mitochondrial disorder?

Answer 10

Muscle (especially), brain, retina