Mitochondrial Biology and Genetics

Question 1

Mitochondria are more abundant in cells with …

Answer 1

high energy requirements

Question 2

The mitochondrial genome is a closed supercoiled circular double-stranded DNA molecule
that is 16,569 bp in length. The GC content is about 44% overall. One strand containts significant more guanine residues, while the other contains more cytosine residues. Whare these starnds called?

Answer 2

The strand with more guanine residues has a heavier molecular weight and is called the heavy (H) strand. The other strand has more cytosine residues and is called the light (L) strand.

Question 3

What is the control region of mitochondrial DNA?

Answer 3

The D-loop region which is a small region of triple-stranded DNA (with 2 copies of the H strand).

This region has promoters and O_H (heavy strands)

Question 4

Which enzyme catalyzes replication of mitochondrial DNA and where is it encoded?

Answer 4

• DNA polymerase gamma (Y)
• it is encoded by the nuclear genome

Question 5

Unlike nuclear genes, the mitochondrial genome is
extremely compact, with 93% of it representing coding
sequences.
There are 2 non-coding regions within the contorl region of the mtDNA. What are these regions called?

Answer 5

hypervaribale regions/segments

These regionas show considerable polymorphism

Question 6

Is the mutation rate higher in the nuclear or mitochondrial genome?

Answer 6

mitochondrial genome
The mutation rate of the mitochondrial genome is
about 10 times higher than that of the nuclear
genome.

Most mitochondrial mutatiosn are transitions. Transition, in genetics and molecular biology, refers to a point mutation that changes a purine nucleotide to another purine (A ↔ G), or a pyrimidine nucleotide to another pyrimidine (C ↔ T)

Question 7

Where do promoters for the mitochondrial genome reside?

Answer 7

D-loop region

Question 8

How many genes does the mitochondrial genome contain?

Answer 8

37

Question 9

Mitochondrial genes code for their own …

Answer 9

• tRNAs
• rRNAs
• some of the subunits of complexes I, III, IV, V

those are the complexes that are part of OxPhos

Question 10

Many of the proteins that act within the mitochondria are nuclear in origin. These proteins must be transported in to the mitochondria. What are nuclear encoded mitochondrial proteins called? And what do these proteins have that helps target these proteins to the mitochondria?

Answer 10

• mitochondrial precursor proteins
• signal sequence

Question 11

Two mitochondrial translocators are needed to ransport proteins into the mitochondrial matrix. What are these called?

Answer 11

• TOM complex (translocator of the outer membrane)
• TIM23 complex (translocator of the inner membrane)

Question 12

The transport of proteins into the mitochondria against their concentration gradients require what situation?

Answer 12

An electrochemical H⁺ gradient across the inner membrance, which is maintained by the pumpingof H⁺ from the matrix into the intermembrane space driven by the elctron transport process in the inner membrane.

Question 13

What are the roles of the chaperone proteins of the hsp70 family?

Answer 13

• keep mitochondrial precursor proteins in the unfolded configuration in the cytoplasm
• prevent aggregation of the precursor proteins
• assure correct folding of imported proteins

these processes require hydrolysis of ATP to ADP

Question 14

Most mitochondrial proteins are encoded by nuclear genes.
True or False?

Answer 14

True

Question 15

The theory that proses that organelles of modern eukaryotic cells, such as mitochondria and chloroplasts, is a consequence of the envelopment of ancient bacteria by early eukaryotic cells is called …

Answer 15

the Endosymbiotic Theory

Question 16

Which one group of the following genes/sequences is not present in the mitochondrial genome?
- mitochondrial enzyme genes
- mitochondrial membrane transporter genes
- non-coding sequences
- rRNA genes
- tRNA genes

Answer 16

mitochondrial membrane transporter genes

Question 17

Which one of the following genetic elements is absent in the mitochondrial genome?
- origin of replication
- protein coding sequence
- promoter
- ribosomal RNA gene
- telomere

Answer 17

telomere

Question 18

Which one of the following is part of the mitochondrial genome?
- centromere
- intron
- long-interspersed sequences (LINEs)
- polyadenylation signal
- telomeres

Answer 18

polyadenylation signal

Question 19

Which one of the following proteins is not required for mitochondrial protein import and processing?
- carnitine-palmitoyl transferase I
- chaperone Hsp70
- mitochondrial signal peptides
- translocator of the outer membrane
- translocator of the inner membrane

Answer 19

carnitine-palmitoyl transferase I

Question 20

Which of the oxidative phosphorylation enzyme complexes are partly constituted by a mitochondrially-encoded gene product?

Answer 20

Complex I
Complex III
Complex IV
Complex V

Question 21

Which one of the following is NOT required to help target a protein synthesized in the cytoplasm to the mitochondrial matrix?
- an electrochemical H⁺ gradient across the inner membrance
- cytochrome oxidase
- matrix targeting sequence of the N-terminal
- translocator of the inner membrane
- tranlocator of hte outer membrane

Answer 21

cytochrome oxidase

Question 22

Whcih one of the following cannot explain why the mutation rate in mitochondrial DNA is much higher than that of nuclear DNA?
- mitochondrial DNA is in close proximity to reactive oxidative species
- mitochondrial DNA is not protected by histones
- mitochondrial DNA repair is very limited
- mitochondrial DNA is triple-stranded in some areas

Answer 22

mitochondrial DNA is triple stranded in some areas

Question 23

Which one of hte follwoing molecules functioning in the mitochondria is encoded by the nuclear genome?
- DNA ploymerase y (gamma)
- ribosomal RNA
- transfer RNA

Answer 23

DNA polymerase y (gamma)

Question 24

Which one of the following statements about human mitochondria is true?
- mitochondrial genes are inherited from both maternal and paternal sources
- most mitochondrial proteins are ncoded by nuclear genes
- rRNA and tRNA are imported from the cytoplasm and used in mitochondrial protein synthesis
- the mitochondrial genome encodes for all proteins found in teh mitochondria
- the mitochondrial genome is not subject to mutations

Answer 24

most mitochondrial proteins are encoded by nuclear genes