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Name: The Neurospora octad shown came from across between mt and m' strains.
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Description: The Neurospora octad shown came from across between mt and m' strains.a. Is this an MI or an MIl octad or neither?Explain.b. Diagram the production of this octad.c. Is it possible to observe evidence ofheteroduplex formation in a Neurosporaascus even

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Biology

m' m³ m* m m* m-

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter19: Genomes And Proteomes

Section: Chapter Questions

Problem 8TYK

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4. A recent estimate of the rate of base substitutions atSNP loci is about 1 × 10−8 per nucleotide pair pergamete.a. Based on this estimate, about how many de novomutations (that is, mutations not found in the genomes of your parents) are present in your own genome?b. Where and when did these de novo mutations inyour genome most likely occur?
0. Indicate which of the four major classes of rearrangements (deletions, duplications, inversions, and translocations) are most likely to be associated with each of thefollowing phenomena. In each case, explain the effect.a. semisterilityb. lethalityc. vulnerability to mutation
8. As explained in the text, the cause of many geneticdiseases cannot yet be discerned by analyzing wholeexome/genome sequences. But in some of theseseemingly intractable cases, important clues can beobtained by looking at mRNAs or proteins, ratherthan at the DNA.a. As you will see in more detail in later chapters, it ispossible to use single-molecule methods to sequence cDNA copies of millions of mRNA molecules from any particular tissue cheaply. Howcould you sometimes use such information to finda disease gene? When would this information benoninformative?b. A technique called Western blotting allows you toexamine any protein for which you have an antibody; it is possible to see differences in size oramount of that protein. How could you sometimesuse such information to find a disease gene? Whenwould this information be noninformative?
A recent estimate of the rate of base substitutions atSNP loci is about 1 × 10−8 per nucleotide pair pergamete.a. Based on this estimate, about how many de novomutations (that is, mutations not found in the genomes of your parents) are present in your own genome?b. Where and when did these de novo mutations inyour genome most likely occur?c. It has been calculated that each sperm made in a25-year-old man is the result on average of about300 rounds of cell division, starting with the firstmitotic division of the male zygote. In contrast,each mature oocyte found in a 5-month-old femalehuman fetus is the result of about 25 rounds of division, starting with the first mitotic division of thefemale zygote. What bearing do these calculations have on the estimate of the rate of base substitutions in humans, and on your answer to part (b)?
After mutagenesis of wild type Vibrio fisheri, you isolate two different mutant strains (A and B) that, unlike the wild type cells, fail to luminesce when grown to high density in a flask with appropriate medium. Curiously, however, when you inoculate both mutant strains in the same flask, you observe that the mixed (A+B) culture begins to emit light after growing dense. a) What gene/functions are likely affected in each of the two mutants? b) How does this explain their phenotypes?
2. a. You want to create a genetic construct that will express GFP in Drosophila. In addition to the GFPcoding sequence, what DNA element(s) must youinclude in order to express this protein in flies if theconstruct were integrated into the Drosophila genome? Where should such DNA element(s) be located? How would you ensure that GFP is expressedonly in certain tissues of the fly, such as the wing?b. Suppose you insert the GFP coding region plus allof the DNA elements required by the answer to part(a)—except the enhancer—between inverted repeatsfound at the ends of a particular transposable element.Because all of the DNA sequences located betweenthese inverted repeats can move from place to placein the Drosophila genome, you can generate manydifferent fly strains, each with the construct integrated at a different genomic location. You now examine animals from each strain for GFPfluorescence. Animals from different strains showdifferent patterns: some glow green in the eyes,others in…
12. a. You want to create a genetic construct that will express GFP in Drosophila. In addition to the GFPcoding sequence, what DNA element(s) must youinclude in order to express this protein in flies if theconstruct were integrated into the Drosophila genome? Where should such DNA element(s) be located? How would you ensure that GFP is expressedonly in certain tissues of the fly, such as the wing?b. Suppose you insert the GFP coding region plus allof the DNA elements required by the answer to part(a)—except the enhancer—between inverted repeatsfound at the ends of a particular transposable element.Because all of the DNA sequences located betweenthese inverted repeats can move from place to placein the Drosophila genome, you can generate manydifferent fly strains, each with the construct integrated at a different genomic location. You now examine animals from each strain for GFPfluorescence. Animals from different strains showdifferent patterns: some glow green in the eyes,others in…
4. You can carry out matings between an Hfr and F−strain by mixing the two cell types in a small patch ona plate and then replica plating to selective medium.This methodology was used to screen hundreds of different cells for a recombination-deficient recA− mutant. Why is this an assay for RecA function? Wouldyou be screening for a recA− mutation in the F− or Hfrstrain using this protocol? Explain.
6. Explain why both deoxyribonucleoside triphosphates (dNTPs) and dideoxynucleosidetriphosphates (ddNTPs) are used in a Sanger sequencing reaction, with the dNTPs in largeexcess over the ddNTPs.
Robert Bost and Richard Cribbs studied a strain of E. coli (araB14)that possessed a nonsense mutation in the structural gene that encodes Lribulokinase,an enzyme that allows the bacteria to metabolize the sugararabinose (R. Bost and R. Cribbs. 1969. Genetics 62:1–8). From thearaB14 strain, they isolated some bacteria that possessed mutations thatcaused them to revert back to the wild type. Genetic analysis of theserevertants showed that they possessed two different suppressormutations. One suppressor mutation (R1) was linked to the originalmutation in L-ribulokinase and probably occurred at the same locus. Byitself, this mutation allowed the production of L-ribulokinase, but theenzyme produced was not as effective in metabolizing arabinose as theenzyme encoded by the wild-type allele. The second suppressormutation (SuB) was not linked to the original mutation. In conjunctionwith the R1 mutation, SuB allowed the production of L-ribulokinase, butSuB by itself was not able to suppress the…
In addition to Tc1, the C. elegans genome contains otherfamilies of DNA transposons such as Tc2, Tc3, Tc4, andTc5. Like Tc1, their transposition is repressed in thegerm line but not in somatic cells. Predict the behaviorof these elements in the mutant strains where Tc1 is nolonger repressed due to mutations in the RNAi pathway.Justify your answer.
Mutations at simple sequence repeat (SSR) loci occurat a frequency of 1 × 10−3 per locus per gamete,which is much higher than the rate of base substitutions at SNP loci (whose frequency is about 1 × 10−8per nucleotide pair per gamete).a. What is the nature of SSR polymorphisms?b. By what mechanism are these SSR polymorphismslikely generated?c. Copy number variants (CNVs) also mutate at a relatively high frequency. Do these mutations occurby the same or a different mechanism than thatgenerating SSRs?d. The SSR mutation rate is much higher than themutation rate for new SNPs. Why then have geneticists recorded more than 50 million SNP loci butonly about 100,000 SSR loci in human genomes?