Chromatin

Question 1

Chromatin

Answer 1

The filamentous material of chromosomes, comprised of DNA and associated histones and non-histone proteins

Question 2

Specific regions of the genome form connections w/ the nuclear matrix

Answer 2

SARs (scaffold attachment regions) aka MARs (matrix assoc. regions)

Question 3

Organization of Chromatin

Answer 3

• Metaphase chromosome
• scaffold assoc. chromatin
• 30nm solenoid, fibre of packed nucleosomes
• 11nm beads on a string
• DNA double helix

Question 4

The bacterial nucleoid (3)

Answer 4

• DNA complexed w/ basic proteins (not histones, used for compaction)
• highly supercoiled
• tethered to the cell membrane

Question 5

Euchromatin

Answer 5

• gene rich, active portion of genome, appears lightly stained during interphase
• can be Tc active or repressed
• loosely compact

Question 6

Heterochromatin

Answer 6

• darkly stained and tightly packaged throughout the cell cycle, genetically inactive
• constitutive
• facultative

Question 7

Constitutive Heterochromatin

Answer 7

• typically devoid of genes
• always in compact form
• comprised of AT rich repetitive DNA sequence

Question 8

Facultative Heterochromatin

Answer 8

• contains genes that are differentially active/inactive in certain tissues/cells or during certain periods of development
• has potential to be euchromatic

Question 9

DNA methylation

Answer 9

• occurs primarily in C residues that are 5’ to G residues-CpG islands
• found at higher density near gene promoters in vertebrate genomes than would be expected by chance
• methylation is associated w/ repression of gene expression
• 5’methylcytosine