Question 1

Which of the following best explains why the inheritance of leaf color in the four o’clock plant (Mirabilis jalapa) does not follow Mendelian patterns?

Accepted Answer

Leaf color is determined by the genotype of the ovule donor, due to chloroplast inheritance.

Question 2

A cross is made between a poky female (mitochondrial mutant) and a wild-type male in Neurospora. What phenotype will all the progeny display, and why?

Accepted Answer

All progeny will be poky because mitochondria are inherited from the mother.

Question 3

Which of the following statements about mitochondrial DNA (mtDNA) is correct?

Accepted Answer

mtDNA is circular, double-stranded, and generally lacks histone proteins.

Question 4

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 disorder.

Question 5

In yeast, which type of petite mutant results in all progeny being petite when crossed with a normal strain?

Accepted Answer

Suppressive petite

Question 6

Which of the following best describes the concept of heteroplasmy?

Accepted Answer

The presence of more than one type of organellar genome within a cell.

Question 7

A Limnaea snail with genotype Dd (dextral) is produced from a dd (sinistral) mother. What will be the coiling direction of the offspring, and why?

Accepted Answer

Sinistral, because the mother’s genotype determines the phenotype.

Question 8

Which of the following is a real-life example of a human disease caused by mutations in mitochondrial DNA?

Accepted Answer

Leber’s hereditary optic neuropathy (LHON)

Question 9

In Chlamydomonas, the inheritance of streptomycin resistance (strR) is determined by which factor?

Accepted Answer

The mating type of the mt+ parent, due to chloroplast inheritance.

Question 10

Which of the following best explains why high-energy tissues (muscles, heart, brain) are often affected in mitochondrial diseases?

Accepted Answer

These tissues have the highest demand for ATP produced by mitochondria.

Question 11

Which of the following is true regarding the maternal effect in Drosophila embryogenesis?

Accepted Answer

Maternal mRNA and proteins deposited in the egg determine early development.

Question 12

Which equation correctly represents the probability ($$P) of a $$child inheriting a mitochondrial disorder from a heteroplasmic mother, assuming random segregation of mitochondria and a threshold proportion $$t of $$mutant mitochondria is required for disease?

Accepted Answer

$$P = 	ext{probability that mutant mitochondria proportion} \geq t$$

Question 13

Which of the following statements about cpDNA (chloroplast DNA) is correct?

Accepted Answer

cpDNA is circular, double-stranded, and contains genes for photosynthesis.

Question 14

A cross between a white branch ovule and a green branch pollen donor in Mirabilis jalapa produces what type of progeny?

Accepted Answer

All white

Question 15

Which of the following best describes the inheritance pattern of the poky mutation in Neurospora?

Accepted Answer

It is inherited maternally through the cytoplasm.

Question 16

Which of the following is NOT a feature of mitochondrial DNA compared to nuclear DNA?

Accepted Answer

Mitochondrial DNA is packaged with histones.

Question 17

Which of the following best explains why some yeast petite mutants are called 'neutral'?

Accepted Answer

They do not affect the phenotype of progeny when crossed with normal strains.

Question 18

Which of the following is a key difference between nuclear and organellar inheritance?

Accepted Answer

Organellar inheritance is often uniparental (usually maternal), while nuclear inheritance is biparental.

Non-Mendelian and Extranuclear Inheritance: Study Notes for Genetics

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