Examples of histone modifications are acetylation (by histone acetyltransferase, or HAT), which is often linked to gene activation, and deacetylation (by histone deacetylases, or HDACs), which often leads to gene silencing typical of heterochromatin. Such heterochromatinization is initiated from a nucleation site and spreads bidirectionally until encountering boundaries that delimit the silenced areas. Recall from earlier in the text (see Chapter 4) the brief discussion of position effect, where repositioning of the w+ allele in Drosophila by translocation or inversion near heterochromatin produces intermittent w+ activity. In the heterozygous state (w+/w), a variegated eye is produced, with white and red patches. How might one explain position-effect variegation in terms of histone acetylation and/or deacetylation?
Want to see the full answer?
Check out a sample textbook solutionChapter 12 Solutions
EBK CONCEPTS OF GENETICS
- Immortality of Stem cells is supported by the expression of telomerase that can extend the telomere sequence. However, one daughter cell created by division of stem cells will not be immortal due to lack of telomerase expression. What difference will you expect in regulation of the telomerase coding gene between the two daughter cells produced by cell division of stem cells? How might the cells be different in terms of chromatin structure at that loci?arrow_forwardYou would like to add a nuclear localization sequence (NLS) of Lys-Lys-Lys-Arg-Lys to a protein that is usually found in the cytoplasm of a yeast cell. To accomplish this, you introduce the nucleotide sequence encoding the NLS into the gene that encodes the cytoplasmic protein of interest. a. What is the size of the nucleotide insert that will encode the NLS? Briefly explain. 5' 3' b. Below is a diagram of the gene encoding the cytoplasmic protein of interest in the yeast genome. If your goal is to put the NLS at the carboxyl (C) terminus of the protein, at which location (A-E) should the NLS be inserted? Briefly explain. A TATAA ATATT promoter +1 B ATG TAC D TAA ATT stop codon E 3' 5'arrow_forwardDNA methylation is considered an epigenetic phenomenon because the pattern of methylation can be inherited. Briefly discuss the question of whether histone modifications in chromatin represent an epigenetic phenomenon.arrow_forward
- The following image shows the 'beads-on-a-string' model of DNA and the effects of histone modification on chromatin structure. What effect does histone acetylation have on Gene 1? Gene 1 De-acetylation Acetylation Ac Ac Gene 1 Ac Ac Ac O Acetylation increases expression of Gene 1 O Acetylation decreases expression of Gene 1 O Acetylation causes a mutation in Gene 1 O There is no way to tell from this figurearrow_forwardWhy do chromatin remodeling factors exist? Remodeling factors are not essential but help regulate gene expression. Nucleosomes are intrinsically immobile on a biological timescale at physiological conditions. Remodeling factors are essential regulators of gene expression through covalent modification of histone tails.arrow_forwardWhat chemical and structural properties of histones enable them to successfully package eukaryotic DNA? What is chromatin remodeling, and how is it controlled within eukaryotic cells?arrow_forward
- What is meant by the term chromatin remodeling? Describe the importance of this process to transcription.arrow_forwardHistone modifications may typically decrease expression of a gene by removing histone acetylation and [Select] histone methylation, causing the chromatin to become more loosely packed.arrow_forwardYou 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_forward
- Describe how methylation and acetylation of the histones changes gene expression in eukaryotes. What groups are added? How do these processes physically affect chromatin structure? Silencing or Enhancing expression?arrow_forwardHuman Chromosome 22 (48 × 106 nucleotide pairs in length) has about 700 protein-coding genes, which average 19,000 nucleotide pairs in length and contain an average of 5.4 exons, each of which averages 266 nucleotide pairs. What fraction of the average protein-coding gene is converted into mRNA? What fraction of the chromosome do these genes occupy?arrow_forwardGive at least one example of a chromosomal structureor function affected by the following mechanisms formodulating chromatin structure:a. Posttranslational changes of the normal histonesfound in the nucleosomearrow_forward
- Human Anatomy & Physiology (11th Edition)BiologyISBN:9780134580999Author:Elaine N. Marieb, Katja N. HoehnPublisher:PEARSONBiology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxAnatomy & PhysiologyBiologyISBN:9781259398629Author:McKinley, Michael P., O'loughlin, Valerie Dean, Bidle, Theresa StouterPublisher:Mcgraw Hill Education,
- Molecular Biology of the Cell (Sixth Edition)BiologyISBN:9780815344322Author:Bruce Alberts, Alexander D. Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter WalterPublisher:W. W. Norton & CompanyLaboratory Manual For Human Anatomy & PhysiologyBiologyISBN:9781260159363Author:Martin, Terry R., Prentice-craver, CynthiaPublisher:McGraw-Hill Publishing Co.Inquiry Into Life (16th Edition)BiologyISBN:9781260231700Author:Sylvia S. Mader, Michael WindelspechtPublisher:McGraw Hill Education