Chapter 9 Extranuclear Inheritance1) 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 ________.A) sex-linked inheritanceB) neo-Mendelian inheritanceC) extrachromosomal inheritanceD) suppressive inheritanceE) dominance and/or recessivenessAnswer: CSection: Introduction2) Which of the following organelles are involved in the general category of organelle heredity?A) mitochondria and chloroplastsB) golgi and nucleiC) lysosomes and peroxisomesD) F factors and episomesE) golgi and rough endoplasmic reticulumAnswer: ASection: 9.13) To which of the following does the term heteroplasmy refer?A) cells with a variable mixture of normal and abnormal organellesB) heterozygous individuals with more than one gene pair involvedC) conditions in which the germ plasm is a mixture of dominant and recessive genesD) a circumstance that is homologous to incomplete dominanceE) various stages of development of mitochondria and chloroplastsAnswer: ASection: 9.14) Direction of shell coiling in the snail Limnaea peregra is conditioned by a form of extrachromosomal inheritance known as ________.A) sex-linked inheritanceB) heteroplasmyC) maternal effectD) independent assortmentE) epistasisAnswer: CSection: 9.41Copyright © 2012 Pearson Education, Inc.5) What is the expression pattern of dominant-negative mutations in petite strains of yeast?A) Expression of wild-type mitochondria is enhanced.B) Expression of mutant mitochondria resembles expression of wild-type mitochondria.C) Mitochondria show enhanced capacity of oxidative phosphorylation.D) The function of wild-type mitochondria is suppressed.E) Mitochondrial membranes become hyperpolarized.Answer: DSection: 9.26) The maternal effect in Limnaea 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 ________.A) orientation of the spindle apparatus in early cleavageB) genophores present in the egg cytoplasmC) the F factor exerting its influence on the centrosomeD) colicins "poisoning" one of the cleavage centersE) allelic substitution as demonstrated from RNA injection experimentsAnswer: ASection: 9.47) One explanation for organelle inheritance is that ________.A) mitochondria and chloroplasts lack DNA and are therefore dependent on the maternal cytoplasmic contributionsB) mitochondria and chloroplasts have DNA that is subject to mutationC) organelles such as mitochondria are always wild typeD) chloroplasts, for example, are completely dependent on the nuclear genome forcomponentsE) None of the answers listed is correct.Answer: BSection: 9.28) 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?Answer: In Limnaea, the mother's genotype establishes the direction of the first cleavage division and, thus, the direction of shell coiling. During formation of the egg, nutritional as well as informational molecules (RNAs) are placed in appropriate positions for development of the embryo. Results (non-Mendelian) indicate that the direction of coiling is determined by the genotype of the mother, not the genotype of the zygote.Section: 9.42Copyright © 2012 Pearson Education, Inc.9) 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.Female MaleCross #1: lt stw/lt stw lt+stw+/lt stwCross #2: lt+ stw/lt stw lt stw+/lt stwCross #3: lt+ stw+/lt stw lt stw/lt stwAnswer: Cross #1: 1/2 light Malpighian tubes, straw bristles, 1/2 wild typeCross #2: more pigmented Malpighian tubes, 1/2 straw bristlesCross #3: more pigmented Malpighian tubes, 1/2 straw bristlesSection: 9.410) 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?Answer: In cases of extrachromosomal inheritance, because the "maternal" contribution is more significant than the "paternal" contribution, the results are different from those expected from simple Mendelian inheritance. The traits of the offspring are more influenced by the "maternal" contribution.Section: Introduction11) Name two human disorders that appear to be transmitted extrachromosomally.Answer: myoclonic epilepsy and Leber's hereditary optic neuropathySection: 9.312) 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?Answer: Both nuclear and cytoplasmic (mitochondrial) genes contribute to the petite phenotype in some cases. The three categories of petites are segregational, neutral, and suppressive.Section: 9.213) Why is variegation in four o'clock plants determined by the phenotype of the ovule source?Answer: The chloroplasts determine the leaf coloration, and the chloroplasts are inherited through the ovule.Section: 9.23Copyright © 2012 Pearson Education, Inc.14) 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.Answer: Both mitochondria and chloroplasts possess DNA, which directs the synthesis of proteins. These proteins influence mitochondrial structure and function and, thus, influence the phenotype. Mitochondria are involved in energy conversions in cells (petite strains in yeast); chloroplasts are involved in photosynthesis as well as leaf coloration (iojap in maize).Section: 9.2, 9.315) List two classes of extrachromosomal inheritance and give an example of each.Answer: maternal effect, pigmentation in Ephestia kuehniella; organelle heredity, variegation in Mirabilis jalapaSection: 9.2, 9.3, 9.416)