Question 1

Which of the following best describes organelle heredity?

Accepted Answer

Transmission of genetic information through the cytoplasm, usually from one parent, involving DNA in mitochondria or chloroplasts.

Question 2

A cross is performed between a white-branch ovule and a green-branch pollen donor in Mirabilis jalapa. What will be the phenotype of the offspring?

Accepted Answer

All offspring will have white leaves.

Question 3

Which experimental result provided the first evidence for cytoplasmic inheritance in Chlamydomonas?

Accepted Answer

Streptomycin resistance was inherited only from the parent contributing the cytoplasm, not the reciprocal cross.

Question 4

Which of the following is a key feature of mitochondrial DNA (mtDNA) compared to nuclear DNA?

Accepted Answer

mtDNA is typically circular and double-stranded, while nuclear DNA is linear.

Question 5

A slow-growing mutant strain of Neurospora crassa, called 'poky,' is associated with which cellular defect?

Accepted Answer

Absence of several cytochrome proteins needed for electron transport in mitochondria.

Question 6

Which type of petite mutation in Saccharomyces cerevisiae is inherited cytoplasmically and results in all wild-type progeny when crossed with a wild-type strain?

Accepted Answer

Neutral petite

Question 7

According to the endosymbiotic theory, which statement is correct?

Accepted Answer

Mitochondria and chloroplasts originated from free-living bacteria engulfed by ancestral eukaryotic cells.

Question 8

Which of the following is NOT a criterion for attributing a human disorder to a mitochondrial DNA mutation?

Accepted Answer

The disorder must show a Mendelian inheritance pattern.

Question 9

A woman with a mitochondrial disorder has children with a healthy man. What is the expected outcome for their children?

Accepted Answer

All children will inherit the mitochondrial disorder.

Question 10

Which of the following best explains why mitochondrial DNA is more susceptible to mutations than nuclear DNA?

Accepted Answer

mtDNA lacks histone protection and has limited DNA repair mechanisms.

Question 11

Which human disease is associated with mitochondrial DNA mutations and is characterized by myoclonic epilepsy and ragged-red muscle fibers?

Accepted Answer

MERRF (Myoclonic Epilepsy and Ragged-Red Fiber Disease)

Question 12

What is heteroplasmy?

Accepted Answer

The presence of a mixture of normal and mutated organelle DNA within a cell.

Question 13

Which of the following statements about the maternal effect is correct?

Accepted Answer

The phenotype of the offspring is determined by the genotype of the mother, due to gene products present in the egg.

Question 14

In Lymnaea peregra (snail), what determines the direction of shell coiling in the offspring?

Accepted Answer

The genotype of the parent producing the egg.

Question 15

Which of the following best describes the role of nuclear genes in mitochondrial function?

Accepted Answer

Most proteins required for mitochondrial function are encoded by nuclear genes and imported into the mitochondria.

Question 16

A cross between a haploid wild-type and a haploid suppressive petite yeast results in which phenotype in the diploid zygote's progeny?

Accepted Answer

All petite

Question 17

Which of the following is a real-world application of mitochondrial replacement therapy (MRT)?

Accepted Answer

Preventing the transmission of mitochondrial DNA mutations from mother to child.

Question 18

Which ribosomal RNA genes are encoded by chloroplast DNA?

Accepted Answer

$$16S$$ and $$23S$$ rRNA genes

Question 19

Which of the following best explains why mitochondrial dysfunction is implicated in a wide range of human diseases?

Accepted Answer

Mitochondria are essential for aerobic cellular respiration, so defects affect energy production in many tissues.

Extranuclear Inheritance: Organelle Genetics and Maternal Effects

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