Concept explainers
A survey of organisms living deep in the ocean revels two new species whose DNA is isolated for analysis. DNA samples from both species are treated to remove nonhistone proteins. Each DNA sample is then treated with DNase I that cuts DNA not protected by histone proteins but is unable to cut DNA bound by histone proteins. Following DNase I treatment, DNA samples are subjected to gel electrophoresis, and the gels are stained to visualize all DNA bands in a gel. The staining patterns of DNA bands from each species are shown in the figure. The number of base pairs in small DNA fragments is shown at the left of the gel. Interpret the gel results in terms of chromatin organization and the spacing of nucleosomes in the chromatin of each species.
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Genetic Analysis: An Integrated Approach (2nd Edition)
- As shown, telomerase attaches additional DNA, six nucleotides at a time, to the ends of eukaryotic chromosomes. However, it makes only one DNA strand. Describe how the opposite strand is replicated.arrow_forwardThe Polymerase Chain Reaction is a molecular biology tool for exponentially amplifying DNA in a test tube in a cell free system. With this technique, DNA strands are separated by heating the mixture so that a DNA helicase is not required. A heat stable polymerase (Pol Z) is then used to copy DNA over and over in a tube. Recently an improved version of Pol Z was created by fusing Protein X, a DNA binding protein, to Pol Z (see left figure below). The right panel shows that fusion of Pol Z to Protein X significantly increases its efficiency. Briefly provide a plausible mechanism for how Protein X is improving Pol Z. Which prokarotic/eukaryotic protein activity is Protein X mimicking that increases the activity of the polymerase?arrow_forwardYou are interested in studying a gene called pumper that is important for heart function. The pumper gene is only expressed (transcribed) in heart cells, and you think the reason for this may have to do with chromatin structure. To investigate this, you isolate chromatin from heart cells and skin cells, and perform a long digestion of both samples with DNAse I, a non-sequence specific enzyme that will cut the phosphodiester bonds linking adjacent nucleotides. You then remove all proteins and analyze the DNA by gel-electrophoresis. You are able to detect only the DNA fragments that contain the pumper gene. The bands at the top of lane 2 indicate very large DNA fragments that were not able to migrate very far in the gel. The numbers to the left indicate where in the gel DNA fragments of the indicated size would migrate. Based on this data, which of the following is likely to be TRUE regarding the pumper locus in heart cells? (select all that apply) hyper-acetylation of lysine on Histone…arrow_forward
- You have discovered a new species of plant. You isolate chromatin from the plant and examines it with the electron microscope and see characteristic beads on a string structure. After addition of a small amount of nuclease, which cleaves the string into individual beads that each contain 280 bp of DNA. With more digestion a 120-bp fragment of DNA remains attached to a core of histone protein. Analysis of the histone core reveals histones in the following proportions: H2A 33.3% H2B 33.3% H3 0% [no histone H3 found] H4 33.3% Based on these observations, what conclusions can you make about the probable structure of the nucleosome in the chromatin of this plant? Be specific in describing the nature of the nucleosome: which histones form the core (), how many of each are present () and size in bp of core-DNA that envelopes it ().arrow_forwardThe regulation of replication is essential to genomic stability. Normally, the DNA is replicated just once in every eukaryotic cell cycle (in the S phase). Normal cells produce protein A, which increases in concentration in the S phase. In cells that have a mutated copy of the gene encoding protein A, the protein is not functional, and replication takes place continuously throughout the cell cycle, with the result that cells may have 50 times the normal amount of DNA. Protein B is normally present in G1, but disappears from the cell nucleus during the S phase. In cells with a mutated copy of the gene encoding protein A, the levels of protein B fail to drop in the S phase and, instead, remain high throughout the cell cycle. When the gene for protein B is mutated, noreplication takes place. Propose a mechanism for how protein A and protein B might normally regulate replication so that each cell gets the proper amount of DNA. Explain how mutation of these genes produces the effects just…arrow_forwardIn chromosomes, doubly-stranded DNA wraps tightly around histone proteins. Think about the structure of DNA, especially the "backbone," and determine what category of amino acids make up the majority of histones: Histone Octamer tetramer dimer HZA dimer dimer dimer Histone "fastener" Here the blue represents histones, and the red is the DNA strand. To help the DNA fold up in an aqueous environment, the histones are nonpolar to exclude water, so many of the amino acid side chains are nonpolar. The backbone of DNA is the alternating phosphate-sugar part, and the phosphate is negatively charged. Positive charges on the histone residues will bind tightly here, so the acidic amino acids are used here. The backbone of DNA is the alternating phosphate-deoxyribose part, and the phosphate is negatively charged. Positive charges on the histone residues will bind tightly here, so the basic amino acids are used here. The histones are strongly attracted to the hydrogen-bonding of the base pairs, so…arrow_forward
- In some organisms, UV-induced thymine dimers can be repaired by photoreactivation, in which energy from visible light is used to split the bonds forming the cyclobutane ring ? true or false Non-homologous end joining occurs when enzymes cut out a few nucleotides around a double strand DNA break, and then fuse the ends back together (right) true or false?arrow_forwardWhich of the following is/are true of DNA general recombination? The process involves invasion of a single-stranded DNA with a free 3'-end into a DNA duplex with the same sequence (on one strand) The process involves formation and resolution of a Holliday structure. The process involves use of a restriction endonuclease. The process involves synthesis of DNA by DNA polymerase.arrow_forwardWhat causes the change in the ability of DNA to absorb UV light when it is denatured? options: In denatured DNA, DNA double helix is disrupted, which causes the exposure of the deoxyribose and thus increases their absorbance of UV light In denatured DNA, DNA double helix is disrupted, which causes the exposure of the phosphate groups and thus increases their absorbance of UV light. In denatured DNA, DNA double helix is disrupted, which causes the exposure of the bases and thus increases their absorbance of UV light. all of the above are correctarrow_forward
- Each peak in a chromatogram corresponds to: A fluorescent ddNTP which has been released from the DNA fragment resulting in the termination of synthesis A fluorescent dNTP which has been released from the DNA fragment resulting in the termination of synthesis A fluorescent dNTP which has been incorporated into the DNA fragment resulting in the termination of synthesis. A fluorescent ddNTP which has been incorporated into the DNA fragment resulting in the termination of synthesisarrow_forwardSupercoiled DNA is slightly unwound compared to relaxed DNA and this enables it to assume a more compact structure with enhanced physical stability. Describe the enzymes that control the number of supercoils present in the E. coli chromosome. How much would you have to reduce the linking number to increase the number of supercoils by five?arrow_forwardDuring template-directed synthesis of a new DNA strand it can happen, if there are simple repeated sequences, that either the template strand or the strand being synthesized "slips" a short distance, and this can change the number of repeating sequence units in that stretch of repeated sequence. Which of the following processes involve such slippage? More than one answer is correct. Options: The increase in genomic copy number of a DNA transposon by transposition from a location behind a replication fork to a location ahead of the fork. Introduction of indels during DNA replication. The initial unwinding of the DNA duplex during replication by helicase. Increasing lengths of CAG trinucleotide repeats in the huntingtin gene giving rise to Huntington disease. Synthesis of primer by primase during DNA replication.arrow_forward
- Biology Today and Tomorrow without Physiology (Mi...BiologyISBN:9781305117396Author:Cecie Starr, Christine Evers, Lisa StarrPublisher:Cengage Learning