Module 8 Lec 6

Question 1

What is the mutation rate of mtDNA compared to nuclear DNA?

Answer 1

mtDNA has a mutation rate about 10 times higher than nuclear DNA.

Question 2

Why is the high mutation rate in mtDNA important?

Answer 2

It leads to more species differences over time, making mtDNA useful for evolutionary studies

Question 3

How is mtDNA used in evolutionary studies?

Answer 3

mtDNA helps study evolutionary relationships among closely related organisms.

Question 4

What can mtDNA trace in human evolution?

Answer 4

mtDNA traces the maternal lineage of humans, back to a few women who lived about 130,000 years ago.

Question 5

How is mtDNA used in forensic science?

Answer 5

mtDNA is used in Argentina courts for identifying biological relationships and tracing ancestry.

Question 6

How many mitochondrial genomes are present in each cell?

Answer 6

Cells contain several mitochondria, each with dozens to thousands of mitochondrial genomes.

Question 7

Do all mitochondrial genomes in a cell have the same sequence?

Answer 7

No, the genomes can differ and do not have to be identical.

Question 8

How do mitochondria divide?

Answer 8

Mitochondria divide by binary fission, with genomes being distributed randomly

Question 9

What happens to mutant and wild-type mitochondrial genomes during cell division?

Answer 9

Daughter cells can inherit different proportions of mutant and wild-type mitochondrial genomes.

Question 10

Is mitochondrial inheritance Mendelian?

Answer 10

No, mitochondrial inheritance is non-Mendelian.

Question 11

Can we use the terms “heterozygous” or “homozygous” for mitochondrial inheritance?

Answer 11

No, these terms do not apply to mitochondrial inheritance.

Question 12

What does it mean when all copies of the mitochondrial genome are identical?

Answer 12

It is called homoplasmic.

Question 13

What does it mean when one or more copies of the mitochondrial genome are different?

Answer 13

It is called heteroplasmic.

Question 14

What type of inheritance is common for mitochondrial DNA (mtDNA)?

Answer 14

Uniparental and maternal inheritance.

Question 15

What was observed in the study with Xenopus mtDNA?

Answer 15

In F1 hybrids, the offspring retain only mtDNA from the mother.

Question 16

How was the maternal inheritance of Xenopus mtDNA tested?

Answer 16

Purified mtDNA from two species was hybridized to probes from the same species, showing maternal inheritance.

Question 17

What is one possible mechanism of uniparental inheritance?

Answer 17

Differences in gamete size, where the larger female gamete contributes the organelles.

Question 18

How does the male gamete’s organelles contribute to inheritance in some species?

Answer 18

n some organisms, male gametes’ organelles degrade, preventing paternal mtDNA inheritance.

Question 19

What happens to paternal organelles in some plants?

Answer 19

Paternal organelles are distributed to cells that will not become part of the embryo.

Question 20

How does the zygote handle paternal organelles after fertilization in some species?

Answer 20

The zygote destroys paternal organelles shortly after fertilization.

Question 21

How do some organisms exclude paternal organelles?

Answer 21

In some species, paternal organelles are excluded from the female gamete during fertilization

Question 22

What is Leber’s hereditary optic neuropathy (LHON)?

Answer 22

LHON is a mitochondrial genetic disorder that causes optic nerve degeneration and blindnes

Question 23

What causes the severity of LHON?

Answer 23

The severity of LHON can vary due to random distribution of mitochondria, affecting the efficiency of the respiratory chain.

Question 24

What is the hypothesis regarding mtDNA mutations and aging?

Answer 24

The hypothesis is that accumulation of mutations in mtDNA and biased replication of deleted mtDNA contribute to age-related decline in oxidative phosphorylation.

Question 25

How does aging affect mitochondrial DNA in heart tissue?

Answer 25

The percentage of heart tissue with mitochondrial deletions increases with age.

Question 26

How is mitochondrial dysfunction related to Alzheimer’s disease?

Answer 26

Brain cells from Alzheimer’s patients show abnormally low energy metabolism, with 20-35% of mitochondria carrying mutations in cytochrome c oxidase genes.

Question 27

How does the mutation rate of mtDNA compare to nuclear DNA?

Answer 27

Somatic mutations in mitochondrial DNA are higher than in nuclear DNA.

Question 28

How does mitochondrial oxidative phosphorylation relate to free radicals?

Answer 28

Mitochondrial oxidative phosphorylation produces more free radicals, which are implicated in aging and cellular damage.