Question 1

One explanation for organelle inheritance of disease phenotypes is that____ .

Accepted Answer

Mitochondria and chloroplasts both have DNA and can be subject to mutations, which can lead to inheritance of disease phenotypes. This is supported by numerous genetic and molecular studies.

Question 2

Which of the following is false?

Accepted Answer

Maternal effect involves the phenotype of the offspring being determined by the genotype of the mother, not the offspring inheriting the mother's genotype. The mother's genotype influences the phenotype of the offspring through the cytoplasmic factors present in the egg.

Question 3

The genes for light eyes lt; light and straw bristles stw; straware 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.

Accepted Answer

The answer of The genes for light eyes lt; light...

Question 4

Molecular/structural orientations gradients in an egg are thought to play a significant role in development.What is the origin of such gradients?

Accepted Answer

During the formation of the egg, various molecules such as RNAs and nutrients are placed in specific positions and concentrations that create molecular gradients. These gradients then play a significant role in the development of the embryo.

Question 5

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

The accumulation of mutations in mtDNA appears to be involved in the suspected phenomenon of the decline of mitochondrial function and aging. This is because mtDNA is particularly vulnerable to mutations due to its close proximity to reactive oxygen species generated during oxidative phosphorylation. Over time, these accumulated mutations can impair the ability of the mitochondria to produce energy efficiently, leading to age-related declines in physiological function.

Question 6

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 during early cleavage is known to determine the direction of shell coiling in Lymnaea. This suggests that the maternal effect is a result of factors present during oogenesis that influence spindle orientation in the egg.

Question 7

Axis development is determined by a MATERNAL EFFECT gene in Drosophila.A dominant Bicoid allele is required to set up the correct axis development in flies.bb two loss of function alleles is LETHAL in this MATE EFFECT gene. A female Drosophila named Eustacia had all dead offspring.What is Eustacia's GENOTYPE?

Accepted Answer

Since Eustacia had all dead offspring due to a maternal effect gene, and knowing that bb (two loss of function alleles) is lethal in this context, Eustacia must have the genotype bb. This is because the maternal effect gene's phenotype in the offspring is determined by the mother's genotype, not the offspring's genotype.

Question 8

Approximately one in 5000 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 replacement therapy involves transferring nuclear DNA from the affected cell to a donated egg cell that has healthy mitochondria. This can help prevent the transmission of mitochondrial DNA disorders to future generations. This approach has already been used successfully in some cases and is being researched further as a potential treatment option for mtDNA-based human disorders.

Question 9

In MATERNAL EFFECT,which of the following is TRUE?

Accepted Answer

The answer of In MATERNAL EFFECT,which of the following is...

Question 10

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

Accepted Answer

The evidence that the maternal genotype is involved in providing molecular/structural orientation gradients in eggs is that non-Mendelian results indicate that the direction of shell coiling in snails is determined by the genotype of the mother, not the genotype of the zygote. This suggests that the mother is providing some kind of molecular or structural gradient in the egg that influences the development of the offspring.

Question 11

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 most directly influenced by the genotype of the mother, as this trait is maternally inherited.

Question 12

Which criterion below does not indicate that a human disorder may be attributable to genetically altered mitochondria?

Accepted Answer

The mode of inheritance (whether it is passed down more readily to male or female offspring) does not necessarily indicate whether a disorder is attributable to genetically altered mitochondria. The other options all suggest a potential link to mitochondrial genetic alterations.

Question 13

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

Accepted Answer

LHON is characterized by cytoplasmic inheritance, specifically caused by lesions in mitochondrial DNA. It is inherited from the mother due to the fact that only the egg contributes mitochondria to the developing embryo. The transmission of LHON does not follow the normal pattern of Mendelian inheritance.

Question 14

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

Accepted Answer

Maternal effect refers to the influence of the mother's genotype on the phenotype of her offspring. In the case of Lymnaea peregra, the direction of shell coiling is determined by the mitochondrial DNA inherited from the mother, making it a form of extrachromosomal (outside of the nucleus) inheritance. Therefore, the correct answer is B, as this type of inheritance is responsible for the shell coiling direction.

Question 15

Name two human disorders that appear to be transmitted extrachromosomally.

Accepted Answer

Myoclonic epilepsy and ragged red fiber disease and Leber's hereditary optic neuropathy are both examples of human disorders that appear to be transmitted extrachromosomally. Duchenne muscular dystrophy and Down syndrome are both caused by chromosomal abnormalities, cri-du-chat syndrome is caused by a deletion on chromosome 5, Leber's hereditary optic neuropathy is already mentioned in option D, and pokey chromosome syndrome and kidney cancer do not appear to be transmitted extrachromosomally. Reactive oxygen syndrome is not a known human disorder.

Question 16

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?

Accepted Answer

Kearns-Sayre syndrome is caused by deletions in mitochondrial DNA (mtDNA), which result in a decrease in the overall amount of mtDNA and an increase in the proportion of defective mtDNAs. This leads to impaired oxidative phosphorylation and the symptoms of the disease. The other choices listed are not related to the genetic basis of this disease.

Quiz 9: Extranuclear Inheritance