TMC 3 Flashcards
How long is the human genome?
2m
Describe the structure of the nucleosome.
Histone octamer plus the DNA surrounding it
Describe the structure of histones.
Proteins that DNA is wound around
~146bp wound around histone octamers which are made up of H3, H4, H2A, H2B.
H3 forms a dimer with H4
H2A forms a dimer with H2B
H1 is not part of the nucleosome or histone octamer - it functions as a linker protein to condense the nucleosomes and draw them closer together
Describe the structure of chromatin.
Nucleosome plus H1 TFs plus other proteins
What are the functions of chromatin?
Compaction and organisation of DNA
Regulation of gene expression
How is H1 different from the other histones?
Not part of the nucleosome
Functions as a linker protein
Induces tighter DNA wrapping around nucleosome and compacts DNA further
Stabilises both nucleosome structure and higher-order chromatin architecture
Explain how histone tails can be modified.
N terminal tails can be exposed
Three alpha helices
C terminal tails
What modifications can be added to the tails of histones and where are these added?
N-terminal tail modification
Arginine - methylated
Serine and threonine - phosphorylated
Lysine - methylated, acetylated, ubiquinated, ribosylated, and sumolayted
What amino acids can be modified in histone tails?
Arginine
Threonine
Serine
Lysine
What is euchromatin and heterochromatin?
Euchromatin - loosely compacted, 10nm, accessible genes
Heterochromatin - tightly compacted, 30nm, inaccessible genes
Explain what is meant by the phrase “chromatin states are dynamic”?
Sections of chromatin are regularly remodelled from euchromatin to heterochromatin and vice versa
What is meant by chromatin remodelling?
Changing from euchromatin structure to heterochromatin structure
