Question 1

Which of the following organelles are involved in the general category of organelle heredity?

Accepted Answer

Organelle heredity refers to the inheritance of genetic material from organelles like mitochondria and chloroplasts. Both of these organelles contain their own DNA and have the ability to replicate independently of the nucleus. The other organelles listed (golgi, nuclei, lysosomes, peroxisomes, rough endoplasmic reticulum) do not have their own DNA and are not involved in organelle heredity. Factors and episomes are also not organelles and not involved in organelle heredity.

Question 2

The maternal effect in Lymnaea is such that the genotype of the egg determines the direction of shell coiling regardless of the genotype of the offspring.Apparently,the cause of this spectacular maternal effect results from ________.

Accepted Answer

The orientation of the spindle apparatus in early cleavage determines the direction of shell coiling, as the spindle determines the placement of cells that will form the embryo's left and right sides. This orientation is determined by maternally-inherited factors, which result in the maternal effect observed in Lymnaea.

Question 3

Through the study of mitochondrial disorders,scientists have suggested a link between the decline of mitochondrial function and aging.What process appears to be involved in this suspected phenomenon?

Accepted Answer

Mitochondrial disorders are caused by mutations in the mtDNA, which leads to a decline in mitochondrial function. The accumulation of mutations in the mtDNA is therefore implicated in aging as well, suggesting that the decline in mitochondrial function plays a role in the aging process.

Question 4

List three organisms that provide examples of organelle heredity.

Accepted Answer

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Question 5

Forms of inheritance that do not follow typical Mendelian patterns and that appear to be more influenced by the parent contributing the most cytoplasm to the embryo are grouped under the general heading of ________.

Accepted Answer

Extrachromosomal inheritance is a form of inheritance that does not follow typical Mendelian patterns and is influenced by non-nuclear genetic elements, such as mitochondrial DNA, which are contributed primarily by the maternal parent via the cytoplasm of the egg.

Question 6

Why is variegation in four o'clock plants determined by the phenotype of the ovule source?

Accepted Answer

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Question 7

In what way do mitochondrial mutations influence phenotype?

Accepted Answer

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Question 8

Approximately one in5000 humans either have a mitochondrial DNA disorder or are at risk for developing such a disorder.What future approach involving nuclear transplantation might be available to treat mtDNA-based human disorders?

Accepted Answer

Mitochondrial swapping, also known as mitochondrial replacement therapy, involves replacing the abnormal or mutated mitochondrial DNA in a woman's egg with healthy mitochondrial DNA from a donor's egg. This can potentially prevent the transmission of mitochondrial diseases to future generations. The process involves transferring the nucleus from the woman's egg to a donor egg that has had its nucleus removed, and then fertilizing the reconstructed egg with sperm. The resulting offspring would carry genetic material from three individuals: the mother, the father, and the donor. This approach is still in the experimental stages and has generated ethical concerns.

Question 9

The inheritance of the petite phenotype in yeast is complicated by an interaction of mitochondrial and nuclear genes.What are these complications? Which three categories of petites are commonly described?

Accepted Answer

The answer of The inheritance of the petite phenotype in...

Question 10

Direction of shell coiling in Lymnaea peregra is strongly and most directly influenced by_______.

Accepted Answer

The direction of shell coiling in Lymnaea peregra is strongly and most directly influenced by the genotype of the mother, as this trait is maternally inherited.

Question 11

What is the expression pattern of dominant-negative mutations in petite strains of yeast?

Accepted Answer

Dominant-negative mutations in petite strains of yeast suppress the function of wild-type mitochondria, resulting in reduced ATP production and slower cell growth.

Question 12

Which three classes of macromolecules are encoded by mtDNA?

Accepted Answer

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Question 13

To which of the following does the term heteroplasmy refer?

Accepted Answer

Heteroplasmy refers to cells that have a variable mixture of normal and abnormal organelles, particularly mitochondria. This can result from errors in replication or transmission of mitochondrial DNA during cell division.

Question 14

In what way do chloroplast mutations influence phenotype?

Accepted Answer

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Question 15

How are reciprocal crosses used to identify cases of extrachromosomal inheritance? What criteria would one use to state that a particular mode of inheritance is extrachromosomal?

Accepted Answer

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Question 16

One explanation for organelle inheritance is that ________.

Accepted Answer

Mitochondria and chloroplasts have their own DNA which is subject to mutation. This can lead to differences in organelle function and phenotype that can be inherited from one generation to the next.

Question 17

Researchers in the late 1950s isolated multiple antibiotic-resistant strains of the bacterium Shigella,which causes dysentery.Such resistance was caused by nonchromosomal R factors that originated in E.coli.Which of the following forms of extrachromosomal heredity-maternal effect,organelle heredity,infectious heredity-would you consider most closely related to the transfer bacterial antibiotic-resistant strains?

Accepted Answer

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Question 18

Direction of shell coiling in the snail Lymnaea peregra is conditioned by a form of extrachromosomal inheritance known as ________.

Accepted Answer

Maternal effect inheritance occurs when the maternal genotype determines the phenotype of the offspring, as is the case with the direction of shell coiling in Lymnaea peregra. It is not sex-linked inheritance because the inheritance is not linked to the sex chromosomes, it is not heteroplasmy because that refers to the presence of more than one type of mitochondrial DNA within a cell or organism, it is not independent assortment because that refers to the random separation of chromosomes during meiosis, and it is not epistasis because that refers to the interaction of different genes to affect a phenotype.

Question 19

What is the name of a form of extrachromosomal inheritance that is due to transmission of symbiotic or parasitic microorganisms?

Accepted Answer

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Question 20

How do mitochondria and chloroplasts determine phenotypes? Which characteristics of mitochondria and chloroplasts allow such phenotypes to be inherited? Provide specific examples to illustrate your response.

Accepted Answer

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Quiz 9: Extranuclear Inheritance