Non-Medellin Inheritance Part 2 (Hard)

Questions and Answers

What is the primary reason for the destruction of paternal mitochondria after fertilization?

Paternal mitochondria are larger than maternal mitochondria

Paternal mitochondria have a different DNA structure

Paternal mitochondria are unable to replicate

Paternal mitochondria are modified by ubiquitin, a small regulatory protein (correct)

What is the characteristic of human mitochondrial diseases?

They are caused by environmental factors

They are inherited from the father

They are acute and affect all cells

They are chronic and affect cells requiring high levels of ATP (correct)

What is the consequence of mitochondrial mutations in somatic cells?

They are eliminated from the cell

They are immediately repaired by mitochondrial DNA repair mechanisms

They accumulate as a person ages (correct)

They have no effect on the cell

What is the pattern of transmission of human mitochondrial diseases?

Strict maternal inheritance Signup and view all the answers

What is the significance of heteroplasmy in mitochondrial disease?

It can lead to varying symptoms within a given family Signup and view all the answers

What is the mitochondrial gene mutated in Leber hereditary optic neuropathy?

Any of the above Signup and view all the answers

What is the consequence of a high ratio of mutant to normal mitochondria in a cell?

The cell may exceed a threshold value and express disease Signup and view all the answers

What is the goal of the three-parent baby technology?

To reduce the risk of mitochondrial disease transmission Signup and view all the answers

What is the effect of high oxygen consumption on mitochondrial DNA?

It leads to DNA damage and free radical formation Signup and view all the answers

What is the significance of ubiquitin in the destruction of paternal mitochondria?

It targets paternal mitochondria for destruction Signup and view all the answers

What is the primary function of mitochondria?

Oxidative phosphorylation Signup and view all the answers

How many base pairs are present in the human mitochondrial DNA?

17,000 bp Signup and view all the answers

What is the primary source of mitochondrial proteins?

Nuclear DNA Signup and view all the answers

What is the range of variation in the size of mitochondrial genomes?

400-fold Signup and view all the answers

What is the primary function of the 13 polypeptides encoded by mitochondrial DNA?

Oxidative phosphorylation Signup and view all the answers

What is the size of mitochondrial genomes in plants?

Fairly large Signup and view all the answers

What is the main reason for maternal inheritance of mitochondria in animals?

Destruction of Sperm Mitochondrial DNA Prior to Fertilization Signup and view all the answers

Which of the following organisms exhibits paternal inheritance of mitochondria and chloroplasts?

Gymnosperms (Plants) Signup and view all the answers

What is the primary mechanism of maternal inheritance in Drosophila?

Destruction of Sperm Mitochondrial DNA Prior to Fertilization Signup and view all the answers

In which type of plants is biparental inheritance of mitochondria and chloroplasts observed?

Angiosperms Signup and view all the answers

What is the primary reason for maternal inheritance of mitochondria in mammals?

Lack of Entry of Sperm Mitochondria Signup and view all the answers

Which of the following is NOT a mechanism of maternal inheritance of mitochondria in animals?

Biparental Inheritance Signup and view all the answers

Which species exhibits lack of entry of sperm mitochondria as a mechanism of maternal inheritance?

Chinese hamsters (Cricetulus griseus) Signup and view all the answers

What is responsible for destroying mitochondrial DNA in sperm during maturation in Drosophila?

Endonuclease Signup and view all the answers

Study Notes

Destruction of Sperm Mitochondria After Fertilization

Paternal mitochondria that enter the egg are modified by ubiquitin, a small regulatory protein that targets organelle destruction
This process occurs in most mammals, including humans

Maternal Inheritance of Mitochondria

Human mtDNA is transmitted from the female parent to offspring via the cytoplasm of the egg
Therefore, the transmission of human mitochondrial diseases follows a strict maternal inheritance pattern

Human Mitochondrial Diseases

Over 200 human mitochondrial diseases have been identified
These diseases are typically chronic degenerative disorders affecting cells requiring high levels of ATP, such as nerve and muscle cells
Examples of human mitochondrial diseases include:
- Leber hereditary optic neuropathy, caused by mutations in mitochondrial genes encoding respiratory chain proteins
- Neurogenic muscle weakness, caused by mutations in the ATPase6 gene
- Mitochondrial myopathy and maternal myopathy and cardiomyopathy, caused by mutations in genes encoding tRNA for leucine

Heteroplasmy in Mitochondrial Disease

Heteroplasmy is an important factor in mitochondrial disease, where cells can contain a mixed population of mitochondria, some with disease-causing mutations and others without
The ratio of mutant to normal mitochondria can exceed a threshold value, leading to disease symptoms that may vary widely within a given family

Three Parent Babies

A new reproductive technology has emerged to prevent the transmission of mitochondrial diseases from mothers to their offspring
This technology was pioneered by John Zhang and colleagues in 2016, and involves replacing the mother's mitochondria with those from a donor woman

Mechanisms of Maternal Inheritance

There are three mechanisms responsible for maternal inheritance of mitochondria:
- Lack of entry of sperm mitochondria into the egg
- Destruction of sperm mitochondrial DNA prior to fertilization
- Destruction of sperm mitochondria after fertilization

Sizes of Organellar Genomes

The sizes of organellar genomes vary greatly among different species, with a 400-fold variation in the size of mitochondrial genomes
Mitochondrial genomes are fairly small in animals, intermediate in size in fungi and protists, and fairly large in plants

Mitochondrial DNA

The main function of mitochondria is oxidative phosphorylation, which generates ATP (adenosine triphosphate) for cellular reactions
Human mitochondrial DNA (mtDNA) consists of only 17,000 bp and includes genes for rRNA, tRNA, and 13 polypeptides involved in oxidative phosphorylation
Most mitochondrial proteins are encoded by genes in the nucleus and are made in the cytoplasm before being transported into the mitochondria

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Description

Learn about the destruction of sperm mitochondria after fertilization and the maternal inheritance of mitochondria in humans, including the transmission of mitochondrial diseases.