chapter 17

define DNase I hypersensitive sites. are these regions where transcription occurs or not?

1. DNase I hypersensitive sites - chromatin region that becomes sensitive to digestion by the enzyme DNase 2. If the DNA is tightly packaged, DNase can not come in which also means transcription can not occur

acetylation of histones

1. adds acetyl groups to DNA which causes the positive charge of DNA to be neutralized 2. this causes the DNA to not be as tightly wound around the histone-this would allow transcription to occur 3. acetyltransferase: enzyme adds acetyl groups 4.deacetylase: removes acetyl groups

define chromatin remodeling

1. complex of proteins that bind directly to particular sites on DNA and reposition the nucleosomes, allowing other transcription factors and RNA polymerase to bind to promoters and initiate transcription 2. eukaryotes can shit histones around and move them apart in order to expose a gene that needs to be transcribed

describe how DNA methylation is associated with gene regulation. what gets methylated and how does this result in gene regulation?

1. dna methylation is controlling at the level of transcription. when DNA gets methylated, it attracts deacetylase to the histones which will remove the acetyl groups from the histones and without those, the histones will hold the DNA tightly and transcription will be repressed 2. methyl groups are added to cytosines

define general transcription factors, other transcription factors, basal apparatus, core promoter, and regulatory promoter

1. general transcription factors - necessary for minimal levels of transcription, they bind to the core promoter 2. other transcription factors - regulatory and not essential for transcription 3. basal transcription apparatus - complex made from RNA polymerase, transcription factors, and other proteins that are necessary to carry out transcription

list a few differences between prokaryotic and eukaryotic gene regulation

1. many bacteria and archaeal genes are organized in operons and are transcribed into a single RNA molecule 2. chromatin structure affects gene expression in eukaryotic cells 3. the presence of the nuclear membrane in eukaryotic cells separates transcription and translation

methylation of histones

1. methyl groups are added 2. can package more DNA or less DNA depending on which amino acid of the histones are methylated 3. methyltransferase: enzyme adds methyl groups 4. demthylase: enzyme that removes methyl groups

provide two ways that histones can be modified and describe the effects of these modification as well as the enzymes involved

1. methylation 2. acetylation

define cpG islands

1. stretches of DNA high in guanine and cytosine nucleotides 2. these are there ready to be methylated in the event that transcription needs to be repressed 3. commonly found near transcription start sites

explain the relationship between how tightly packaged DNA is and whether transcription occurs or not

1. when chromatin is in, the RNA polymerase can not find the promoter when the DNA is so tightly wound 2. before transcription, chromatin structures change so that the DNA becomes more accessible to the transcription machinery