Question 1

Describe the molecular and transmission characteristics of Leber's hereditary optic neuropathy (LHON).

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Question 2

Kearns-Sayre syndrome (KSS)results in progressive loss of vision and hearing,as well as heart defects.What is the genetic basis for this disease?

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Question 3

Poky strains in yeast result from suppressive mutations in chloroplast DNA.

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Poky strains in yeast result from suppressive mutations in mitochondrial DNA, not chloroplast DNA. Yeast, like all fungi, do not have chloroplasts. Chloroplasts are found in plant cells and some protists.

Question 4

List three criteria indicating that a human disorder may be attributable to genetically altered mitochondria.

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Question 5

Maternal-effect patterns result when nuclear gene products controlled by the maternal genotype condition the egg and influence early development.Give two examples of maternal effects.

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Question 6

An example of organelle heredity involves pigmentation in Mirabilis jalapa.

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Pigmentation in the flowers of Mirabilis jalapa is controlled by organelle heredity. Specifically, the color of the flowers is determined by the presence or absence of certain pigments that are produced in the plastids (organelles) of the plant's cells. In this case, the pigment responsible for the flower color is not encoded in the plant's nuclear DNA, but is instead inherited from the maternal parent through the cytoplasmic genes of the plastids.

Question 7

The genes for light eyes (lt; light)and straw bristles (stw; straw)are tightly linked on chromosome 2 in Drosophila melanogaster.The Malpighian tubes of lt larvae and adults are maternally affected in that Malpighian tubes of lt/lt organisms,whose mothers were lt⁺/ˡᵗ and have more yellow pigment than those from lt/lt mothers.There is no maternal effect associated with the straw locus.Give the phenotypes of the offspring from the following crosses.
$\begin{array}{lll}
& \underline{\text { Female }} & \underline{\text { Male }} \
\text { Cross \#1: } & l t \text { stw/lt stw } & l t^{+} \text {stw } w^{+} / l t \text { stw } \
\text { Cross \#2: } & l t^{+} s t w / l t \text { stw } & l t \text { stw } w^{+} / l t s t w \
\text { Cross \#3: } &l t^{+} s t w w^{+} / l t \text { stw } & \text { lt stw/lt stw }
\end{array}$

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Question 8

Inheritance of the green and white patches phenotype in Mirabilis jalapa (four o'clocks)is an example of maternal influence.

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Inheritance of the green and white patches phenotype in Mirabilis jalapa (four o'clocks) is not an example of maternal influence. It is an example of incomplete dominance, where the heterozygote (Gg) shows a blended phenotype of both green and white patches. Maternal influence refers to the influence of the maternal environment on the development of the offspring, which is not applicable in this case.

Question 9

What is the meaning of the term endosymbiotic theory?

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Question 10

Molecular/structural orientations (gradients)in an egg are thought to play a significant role in development.What is the origin of such gradients? What evidence indicates that the maternal genotype is involved in providing such gradients?

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Question 11

It appears as if the direction of shell coiling in Lymnaea peregra is influenced by the orientation of the first cleavage division.

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Research has shown that the direction of shell coiling in Lymnaea peregra is indeed influenced by the orientation of the first cleavage division. This phenomenon is known as the Cleavage-Induced Spiral Ornamentation (CISO) hypothesis.

Question 12

Name two human disorders that appear to be transmitted extrachromosomally.

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Question 13

Direction of shell coiling in Lymnaea peregra is influenced by a maternal effect.

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Research has shown that the direction of shell coiling in Lymnaea peregra is influenced by a maternal effect, which means that the mother snail's genes play a role in determining the direction of coiling in the offspring's shell.

Question 14

In what way do segregational petite mutations differ from neutral petites?

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Question 15

Mitochondrial mutations are passed equally to offspring by both males and females.

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Mitochondrial DNA is typically inherited exclusively from the mother, as the mitochondria in the sperm are usually destroyed after fertilization.

Question 16

It is safe to say that a maternal effect is caused by the genotype,not the phenotype,of the parent producing the egg.

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Maternal effect refers to the phenomenon where the phenotype of the offspring is influenced by the genotype of the mother. This means that the genetic information carried by the mother, which is present in the egg, affects the development and phenotype of the offspring. Therefore, it is the genotype of the parent producing the egg that causes the maternal effect, not the phenotype.

Question 17

List two classes of extrachromosomal inheritance and give an example of each.

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Quiz 9: Extranuclear Inheritance