Q&A Hero

Q: One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that their first son will have hemophilia? A) 1/16 B) 1/8 C) 1/4 D) 1/2 E) 3/4

Q: One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem, you must include the probability of having a daughter in your computation of the final probability.) A) 1/16 B) 1/8 C) 1/4 D) 1/2 E) 3/4

Q: A recessive gene for red-green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color blind) marries a color-blind male. What is the likelihood that this couple's first son will be color blind? A) 0% B) 25% C) 50% D) 75% E) 100%

Q: The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female? A) 4:1 male to female B) 2:1 male to female C) 3:1 male to female D) 1:2 male to female E) 1:1 male to female

Q: The Lygaeus mode of sex determination is the ________. A) XY/XX scheme B) XX/XO scheme C) XO/YY scheme D) hermaphroditic scheme E) scheme based on single translocations in the X chromosome

Q: The Protenor mode of sex determination is the ________. A) scheme based on F plasmids inserted into the FMR-1 gene B) XX/XO scheme C) XO/YY scheme D) hermaphroditic scheme E) scheme based on single translocations in the X chromosome

Q: To produce recombinants in bacteria, one crossover is better than two.

Q: Cotransduction of genes is an indication that the genes are linked.

Q: Lysogeny is most likely associated with transduction.

Q: A symbiotic relationship between a phage and a bacterium apparently occurs in the process of lysogeny.

Q: Viral mutations and variants are often categorized by changes in host range and/or plaque morphology.

Q: Lysogeny is a process that occurs during transformation and conjugation.

Q: A plaque is a substance that causes mutation in bacteria.

Q: R plasmids often contain genes for antibody production.

Q: The "interrupted mating technique" provides a genetic map in Drosophila.

Q: An Hfr cell can initiate chromosome transfer from one E. coli to another.

Q: In a bacterial cross in which the donor (Hfr) is a+b+ and the recipient strain (F-) is a-b-, it is expected that recombinant bacteria will all be a+b+.

Q: A form of bacterial recombination that involves a viral intermediate is called ________.

Q: What is a bacteriophage?

Q: Assume that one counted 67 plaques on a bacterial plate where 0.1 ml of a 10-5 dilution of phage was added to bacterial culture. What is the initial concentration of the undiluted phage?

Q: If two different auxotrophic strains are placed in a liquid medium culture tube, prototrophic strains can sometimes be subsequently recovered. Name several mechanisms by which this is possible.

Q: What is a significant difference between a lytic and a lysogenic cycle?

Q: Name three forms of recombination in bacteria.

Q: When a bacteriophage genome incorporates itself into the chromosome of the host, that phage genome is referred to as a(n) ________.

Q: Name the term used to describe the phenomenon in which a bacteriophage genome incorporates its genome into the chromosome of the host.

Q: Bacteriophages that cannot undergo lysogeny but can infect bacteria are called ________.

Q: Compare and contrast bacteriophage lysis and lysogeny.

Q: Lysogeny is an important phenomenon in bacteria and phages. Briefly describe lysogeny (using labeled diagrams if helpful).

Q: What is meant by the term cotransformation?

Q: Explain what is meant by the term heteroduplex in the context of bacterial transformation.

Q: Bacteria that are in a particular physiological state to become transformed are called ________.

Q: Present the general structural features of a plasmid and give an example.

Q: What is the consequence of a mutation in the recA gene in bacteria?

Q: What experimental observation demonstrated that genes are involved in the integration of foreign DNA into the bacterial chromosome?

Q: What are the roles of the recBCD genes?

Q: What is a merozygote?

Q: Describe how different strains of E. coli can reveal different linkage arrangements of genes in Hfr crosses.

Q: What is a form of recombination in bacteria that involves the F plasmid?

Q: What is the role of the F factor in bacterial recombination?

Q: Distinguish between F+ and F- bacteria.

Q: Assume that the gene trpA in an auxotrophic strain of E. coli is located at 27 minutes, whereas the gene pyrE is located at 81 minutes. a) How are minutes arrived at in this context? b) Present an experimental scheme that would allow you to convert one of the auxotrophic strains to a prototrophic strain.

Q: Jacob, Wollman, and others developed a linkage map of E. coli that is based on time. What form of recombination is involved in generating a linkage map based on time?

Q: In what way was the interrupted mating technique used to generate a genetic map in E. coli based on time?

Q: Explain the composition and use of minimal medium in the study of bacterial genetics.

Q: Name the typical phases of the bacterial growth cycle in liquid culture medium.

Q: In general, what two methods are used to grow bacteria in the laboratory?

Q: How does an auxotroph differ from a prototroph?

Q: What are prototrophs?

Q: Name two forms of recombination in bacteria. A) lytic and lysogenic B) auxotrophic and prototrophic C) conjugation and transduction D) mixed and generalized E) insertion and replication

Q: Transduction is a form of recombination in bacteria that involves ________. A) 5-bromouracil B) plasmids C) bacteriophages D) fertility factors E) physical contact between the bacteria involved

Q: Temperate phages are those that can enter either the ________ or ________ cycle. A) lytic; lysogenic B) virulent; avirulent C) functional; nonfunctional D) former; nonformer E) complementing; competing

Q: The clearing made by bacteriophages in a "lawn" of bacteria on an agar plate is called a ________. A) clear zone B) lysogenic zone C) prophage D) plaque E) host range

Q: A bacteriophage that is capable of entering either a lytic or lysogenic cycle is called a(n) ________. A) temperate bacteriophage B) virulent bacteriophage C) plasmid D) episome E) plaque-forming unit

Q: Bacteriophages engage in two interactive cycles with bacteria. What are these cycles? A) lytic and lysogenic B) insertion and replication C) auxotrophic and prototrophic D) heteroduplex and homoduplex E) negative and positive

Q: Name the general category into which double-stranded circular extrachromosomal DNA elements such as F factors, ColE1, and R would fall. A) capsid B) r-determinant C) plaque D) partial diploid E) plasmid

Q: Max Delbrck presented the first evidence that bacteria are capable of spontaneous mutation. What is the name of the test that Delbrck used to demonstrate this phenomenon? A) fluctuation test B) logarithmic test C) lag test D) prototrophic test E) auxotrophic test

Q: If interference is complete, what would be the frequency of double crossovers?

Q: The coefficient of coincidence reflects the frequency of observed double crossovers compared to the frequency of expected double crossovers. What is the relationship between the coefficient of coincidence and interference?

Q: Given that loci A and B in Drosophila are sex-linked and 20 map units apart, what phenotypic frequencies would you expect in male and female offspring resulting from the following crosses? (Assume that A and B are dominant to a and b, respectively.) a) AaBb (dominant alleles on same chromosome) female x ab/Y male b) AaBb (dominant alleles on homologs) female x ab/Y male c) aabb female x AB/Y male (no crossing over in male Drosophila)

Q: Provide a brief definition for positive interference.

Q: Assume that two genes are 80 map units apart on chromosome II of Drosophila and that a cross is made between a doubly heterozygous female and a homozygous recessive male. What percent recombination would be expected in the offspring of this type of cross?

Q: Describe a convenient method for determining gene order from three-point cross results.

Q: (a) In a three-point mapping experiment, what three general classes of offspring are expected (assuming crossovers occur)? (b) How many different genotypic classes are expected?

Q: Three loci, mitochondrial malate dehydrogenase that forms a and b (MDHa, MDHb), glucuronidase that forms 1 and 2 (GUS1, GUS2), and a histone gene that forms + and (H+, H), are located on chromosome #7 in humans. Assume that the MDH locus is at position 35, GUS at position 45, and H at position 75. A female whose mother was homozygous for MDHa, GUS2, and H+and whose father was homozygous for MDHb, GUS1, and Hproduces a sample of 1000 egg cells. Give the genotypes and expected numbers of the various types of cells she would produce. Assume no chromosomal interference.

Q: In the fruit fly, Drosophila melanogaster, a spineless (no wing bristles) female fly is mated to a male that is claret (dark eyes) and hairless (no thoracic bristles). Phenotypically wild-type F1 female progeny were mated to fully homozygous (mutant) males, and the following progeny (1000 total) were observed: a) Which gene is in the middle? b) With respect to the three genes mentioned in the problem, what are the genotypes of the homozygous parents used in making the phenotypically wild-type F1 heterozygote? c) What are the map distances between the three genes? A correct formula with the values "plugged in" for each distance will be sufficient. d) What is the coefficient of coincidence? A correct formula with the values "plugged in" will be sufficient.

Q: Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with what arrangement of genes?

Q: In Drosophila, assume that the gene for scute bristles (s) is located at map position 0.0 and that the gene for ruby eyes (r) is at position 15.0. Both genes are located on the X chromosome and are recessive to their wild-type alleles. A cross is made between scute-bristled females and ruby-eyed males. Phenotypically wild-type F1 females were then mated to homozygous double mutant males, and 1000 offspring were produced. Give the phenotypes and frequencies expected.

Q: Assume that investigators crossed a strain of flies carrying the dominant eye mutation Lobe on the second chromosome with a strain homozygous for the second chromosome recessive mutations smooth abdomen and straw body. The F1 Lobe females were then backcrossed with homozygous smooth abdomen, straw body males, and the following phenotypes were observed: smooth abdomen, straw body 820 Lobe 780 smooth abdomen, Lobe 42 straw body 58 smooth abdomen 148 Lobe, straw body 152 a) Give the gene order and map units between these three loci. b) What is the coefficient of coincidence?

Q: Assume that the genes for tan body and bare wings are 15 map units apart on chromosome II in Drosophila. Assume also that a tan-bodied, bare-winged female was mated to a wild-type male and that the resulting F1 phenotypically wild-type females were mated to tan-bodied, bare-winged males. Of 1000 offspring, what would be the expected phenotypes, and in what numbers would they be expected?

Q: Phenotypically wild-type F1female Drosophila, whose mothers had light eyes (lt) and fathers had straw (stw) bristles, produced the following offspring when crossed to homozygous light-straw males: Compute the map distance between the light and straw loci.

Q: Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism. If you examined 200 primary oocytes, in how many would you expect to see a chiasma between the two loci mentioned above?

Q: The genes for mahogany eyes and ebony body are approximately 25 map units apart on chromosome III in Drosophila. Assume that a mahogany-eyed female was mated to an ebony-bodied male and that the resulting F1 phenotypically wild-type females were mated to mahogany, ebony males. Of 1000 offspring, what would be the expected phenotypes, and in what numbers would they be expected?

Q: What is the relationship between the degree of crossing over and the distance between two genes?

Q: Diagram chromosomal events that will ultimately result in the segregation of alleles (A and a) during meiosis II rather than meiosis I.

Q: At what stage of the meiotic cell cycle and during what chromosomal configuration does crossing over occur?

Q: Under what circumstance might two loci be on the same chromosome but behave as if independently assorting in crosses?

Q: Who was the student in Morgan's laboratory who first realized that the sequence of genes could be determined by Morgan's proposal that two genes located relatively close to each other are less likely to form chiasma between them than if the two genes were relatively far apart?

Q: Based on the classic experiments of Creighton and McClintock with maize, crossing over involves a physical exchange between chromatids. What particular chromosomal characteristic allowed their experiments to succeed? A) colored bands along the lengths of a chromosome B) an extra chromosome C) a missing chromosome D) three chromosomes with identical structure E) a chromosome with a unique cytological marker

Q: What relatively recent scientific advancement has made mapping by linkage or classical genetic mapping approaches virtually obsolete? A) the genome sequence of a species B) the inclusion of the X and Y chromosome in SNP experiments C) the use of synteny D) positive interference E) negative interference

Q: Methods for determining the linkage group and genetic map in humans involve which of the following? A) DNA markers B) twin spots and tetrad analysis C) tetrad analysis and bromodeoxyuridine D) zygotene and pachytene DNA synthesis E) chiasmatype and classical analyses