Q&A Hero

Q: Is the accompanying figure DNA or RNA? Is the circle closer to the 5"² or 3"² end?

Q: During the polymerization of nucleic acids, covalent bonds are formed between neighboring nucleotides. Which carbons are involved in such bonds?

Q: What is the name of the precursor molecule used in nucleic acid synthesis?

Q: Name the pyrimidines and the purines in DNA.

Q: What type of chemical bond holds the two strands together in double-stranded DNA?

Q: Provide an overview of the structure of Z-DNA.

Q: List three forms of DNA.

Q: What does it mean to say that double-stranded nucleic acids are antiparallel?

Q: The base content of a sample of DNA is as follows: A = 31%, G = 31%, T = 19%, C = 19%. What conclusion can be drawn from this information?

Q: (a) Assume that A + T/G + C equals 0.5 in one strand of DNA. What is the ratio of these bases in the complementary strand? (b) If A + G/T + C equals 0.5 in one strand, what is the ratio of these bases in the complementary strand?

Q: Assume that the molar percentage of thymine in a double-stranded DNA is 20. What are the percentages of the four bases (G, C, T, A)? If the DNA is single-stranded, would you change your answer?

Q: If the GC content of a DNA molecule is 60%, what are the molar percentages of the four bases (G, C, T, A)?

Q: What is the difference between a polynucleotide and an oligonucleotide?

Q: List two major differences between RNA and DNA at the level of the nucleotide.

Q: Present an overview of two classical experiments that demonstrated that DNA is the genetic material. Can RNA be the genetic material? Explain.

Q: Beatrice Mintz and others microinjected DNA into a fertilized mouse egg, which after reaching maturity could be transmitted to the mouse's offspring. What is the general term used to describe an organism that incorporates foreign DNA?

Q: What was the Avery et al. (1944) contribution to the understanding of molecular biology?

Q: Briefly define transformation and describe the relationship between the phenomenon of transformation and the discovery that DNA is the genetic material in bacteria.

Q: Experiments conducted in the 1920s by Frederick Griffith involving the bacterium Diplococcus pneumoniae demonstrated that a substance from one bacterial strain could genetically transform other bacterial strains. What was the name of the substance capable of such transformation, and who finally determined its identity?

Q: In the 1860s, a Swiss chemist, Friedrich Miescher, isolated an acidic substance from cell nuclei. What was the name of this substance, and what was its significance?

Q: Considering the Central Dogma of Molecular Genetics, what general property is ascribed to DNA?

Q: Describe four major functions of DNA in a cell.

Q: Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes? A) double-stranded, parallel, (A + T)/C + G) = variable, (A + G)/(C + T) = 1.0 B) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0 C) single-stranded, antiparallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0 D) double-stranded, parallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0 E) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C + T) = variable

Q: In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true? A) A = C B) A = G and C = T C) A + C = G + T D) A + T = G + C E) A = G and C = T and A + C = G + T are both true.

Q: If 15% of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine? A) 15% B) 30% C) 35% D) 40% E) 70%

Q: Considering the structure of double-stranded DNA, which kind(s) of bonds hold one complementary strand to the other? A) ionic B) covalent C) van der Waals D) hydrogen E) hydrophobic and hydrophilic

Q: Regarding the structure of DNA, the covalently arranged combination of a deoxyribose and a nitrogenous base would be called a(n) ________. A) nucleotide B) ribonucleotide C) monophosphate nucleoside D) oligonucleotide E) nucleoside

Q: The basic structure of a nucleotide includes ________. A) amino acids B) tryptophan and leucine C) base, sugar, and phosphate D) mRNA, rRNA, and tRNA E) phosphorus and sulfur

Q: Is the accompanying figure DNA or RNA? ________ Is the arrow closest to the 5"² or 3"² end? ________ Spleen diesterase is an enzyme that breaks the covalent bond that connects the phosphate to the 5"² carbon. Assume that the dinucleotide is digested with spleen diesterase. To which base and to which carbon on the sugar is the phosphate now attached, A or T? A) DNA; 3"² end; T, 5"² B) RNA; 3"² end; A, 3"² C) DNA; 5"² end; A, 5"² D) DNA; 3"² end; A, 3"² E) RNA; 3"² end; T, 3"²

Q: What are the two major components of the Tobacco Mosaic Virus? A) RNA and DNA B) DNA and protein C) RNA and protein D) lipids and nucleic acids E) carbohydrates and nucleic acids

Q: Reverse transcriptase is an enzyme found in association with retroviral activity. It has the property of ________. A) synthesis of DNA from an RNA template B) synthesis of RNA from a DNA template C) requiring no template D) translation E) most lysozymes

Q: In the classic experiment conducted by Hershey and Chase, why was the pellet radioactive in the centrifuge tube that contained bacteria with viruses? A) The bacteria were in the pellet, and they had incorporated radioactive proteins into their cell membranes. B) The radioactive viruses (coats plus DNA) were in the pellet. C) The bacteria were in the pellet, and many contained the radioactive viral DNA. D) The radioactive protein coats of the viruses were in the pellet. E) The radioactive viruses were in the pellet, and the bacteria were in the supernatant.

Q: The classic Hershey and Chase (1952) experiment that offered evidence in support of DNA being the genetic material in bacteriophages made use of which of the following labeled component(s)? A) phosphorus and sulfur B) nitrogen and oxygen C) tritium D) hydrogen E) None of the answers listed are correct.

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

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

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

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

Q: An example of organelle heredity involves pigmentation inMirabilis jalapa.

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

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

Q: 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.

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

Q: 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?

Q: 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 oflt/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 Male Cross #1: lt stw/lt stw lt+stw+/lt stw Cross #2: lt+ stw/lt stw lt stw+/lt stw Cross #3: lt+ stw+/lt stw lt stw/lt stw

Q: 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?

Q: Name two human disorders that appear to be transmitted extrachromosomally.

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

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

Q: What is the meaning of the term endosymbiotic theory?

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

Q: Which three classes of macromolecules are encoded by mtDNA?

Q: 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.

Q: List three organisms that provide examples of organelle heredity.

Q: Why is variegation in four o'clock plants determined by the phenotype of the ovule source?

Q: 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?

Q: In what way do mitochondrial mutations influence phenotype?

Q: In what way do chloroplast mutations influence phenotype?

Q: 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?

Q: What is the name of a form of extrachromosomal inheritance that is due to transmission of symbiotic or parasitic microorganisms?

Q: Researchers in the late 1950s isolated multiple antibiotic-resistant strains of the bacterium Shigella, which causes dysentery. Such resistance was caused by nonchromosomal R factors that originated in E. coli. Which of the following forms of extrachromosomal heredity"maternal effect, organelle heredity, infectious heredity"would you consider most closely related to the transfer bacterial antibiotic-resistant strains?

Q: 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 ________. A) orientation of the spindle apparatus in early cleavage B) genophores present in the egg cytoplasm C) the F factor exerting its influence on the centrosome D) colicins "poisoning" one of the cleavage centers E) allelic substitution as demonstrated from RNA injection experiments

Q: Direction of shell coiling in the snail Lymnaea peregra is conditioned by a form of extrachromosomal inheritance known as ________. A) sex-linked inheritance B) heteroplasmy C) maternal effect D) independent assortment E) epistasis

Q: 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? A) accumulation of sporadic mutations in the nuclear genome B) decline of mutations in the nuclear genome C) accumulation of mutations in the mtDNA D) recombination of mtDNA and nuclear DNA E) recombination among mtDNAs of different mitochondria

Q: Direction of shell coiling in Lymnaea peregra is strongly and most directly influenced by_______. A) the genotype of the mother B) the genotype of the father C) the phenotype of the mother D) the phenotype of the father E) the genotype of the embryo itself

Q: Approximately one in5000 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? A) nuclear disintegration B) mitochondrial swapping C) nuclear activation D) mitochondrial activation E) mitochondrial suppression

Q: One explanation for organelle inheritance is that ________. A) mitochondria and chloroplasts lack DNA and are therefore dependent on the maternal cytoplasmic contributions B) mitochondria and chloroplasts have DNA that is subject to mutation C) organelles such as mitochondria are always wild type D) chloroplasts, for example, are completely dependent on the nuclear genome for components E) None of the answers listed are correct.

Q: 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.

Q: To which of the following does the term heteroplasmy refer? A) cells with a variable mixture of normal and abnormal organelles B) heterozygous individuals with more than one gene pair involved C) conditions in which the germ plasm is a mixture of dominant and recessive genes D) a circumstance that is homologous to incomplete dominance E) various stages of development of mitochondria and chloroplasts

Q: Which of the following organelles are involved in the general category of organelle heredity? A) mitochondria and chloroplasts B) golgi and nuclei C) lysosomes and peroxisomes D) factors and episomes E) golgi and rough endoplasmic reticulum

Q: 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 inheritance B) neo-Mendelian inheritance C) extrachromosomal inheritance D) suppressive inheritance E) dominance and/or recessiveness

Q: In general, inversion and translocation heterozygotes are as fertile as organisms whose chromosomes are in the standard arrangement.

Q: Inversions and translocations are without evolutionary significance.

Q: Translocations may be pericentric or paracentric.

Q: A position effect occurs when a gene's expression is altered by virtue of a change in its position. One might expect position effects to occur with inversions and translocations.

Q: Familial Down syndrome is caused by a translocation involving chromosome 21.

Q: Familial Down syndrome can be caused by a translocation between chromosomes 1 and 14.

Q: Individuals with familial Down syndrome are trisomic and have 47 chromosomes.

Q: A pericentric inversion includes the centromere.

Q: Inversions suppress crossing over by providing a chemical imbalance because of breakpoints within certain genes.

Q: A paracentric inversion is one whose breakpoints do not flank the centromere.