Chapter 18 - Flashcards
What does gene regulation in multicellular eukaryotes lead to?
cell specialisation - different types of cells express different genes
What is the 1st level of gene regulation?
in the chromosome
What is Chromatin?
a complex of DNA, RNA, and proteins that give chromosomes their structure
What is Chromatin remodeling?
the nucleosomes are repositioned to expose different stretches of DNA to the nuclear environment (allows space for transcriptional enzymes and proteins to work)
Chromatin can be remodeled around histone tails - what are histone tails?
strings of amino acids protruding from the histone proteins in the nucleosome (individual amino acids can be modified by the addition)
Where can methylation or acetylation occur?
on lysine residues of histone tails and they can activate or repress transcription
What is a histone code?
pattern of modification of the histone tails - affect chromatin structure and gene transcription
What happens in DNA methylation?
proteins recruited that lead to changes in chromatin structure, histone modification, and nucleosome positioning that restrict access of transcription factors to promoters
WHat are CpG islands?
cluster sof adjacent CG nucleotides located in or near the promoter of a gene
Can the methylation state of a gene change?
yes over time in response to environmental signals (ways to turn on or off a gene)
What is imprinting?
repressed genes by chemical modification of the germ line in a sex specific manner (about 100 in humans and other mammals)
