Biochemistry Flashcards
How does DNA fit into the nucleus?
Chromatin form
What is a nucleosome?
When DNA loops twice around histone octamer
Phosphate gives DNA a +/- charge
-
What gives histones a + charge?
Lysine and arginine
What is the difference between mitochondrial and cellular DNA?
Mitochonddrial is circular and does not utilize histones
Heterochromatin looks like?
Highly condensed
What chromatin is transcriptionally active?
Eurochromatin, heterochromatin isn’t
What does it mean that heterochromatin doesn’t undergo transcription?
Increased methylation and decreased acetylation
What bodies may be in heterochromatin?
Barr bodies (inactive X chromosomes)
Which chromatin is darker?
Heterochromatin
Euchromatin is e
Expressed
What is DNA methylation?
Changes in expression of a DNA segment without changing the sequence
What is DNA methylation involved in?
Aging, carcinogenesis, genomic imprinting, transposable element repression, and X chromosome inactivation
Lyonization
X chromosome inactivation
DNA is methylated in
Imprinting
Methylation within ____ ______ represses gene transcription
CpG islands
Histone methylation causes
Reversible transcriptional suppression, but can also cause activation depending on location of methyl groups
Histone acetylation does what?
Removes histones + charge –> relax DNA coiling and increased transcription
Histone methylation makes DNA mute/active
Histone acetylation makes DNA mute/active
Mute
Active
How do thyroid hormone receptors alter thyroid hormone synthesis?
Acetylation
Nucleoside vs nucleotide
Nucleoside: base + deoxyribose (sugar)
Nucleotide: base + deoxyribose + phosphate linked by 3’=5’ phosphodiester bond
Purine examples
AG - 2 rings
Pyrimidine examples
CUT - 1 ring
Deamination reactions (CAG5)
Cytosine –> Uracil
Adenine –> hypoxanthine
Guanine –> xanthine
5-methylcytosine –> thymine
Uracil is found in ______
Thymine is found in ______
______ of uracil makes thymine
RNA
DNA
Methylation
What end of incoming nucleotide bears the triphosphate ?
5’
What is the purpose of the triphosphate?
Energy source for the bond
What is the target of 3’ hydroxyl attack
a-Phosphate
What has a methyl?
Thymine
Is C-G bond weaker or stronger than A-T bond?
CG (3 H bonds)
AT (2 H bonds)
Increased CG content does what to DNA?
Increases melting temperature of DNA
What are necessary for purine synthesis?
Amino acids (glycine, aspartate, glutamine)
What 2 drugs inhibit pyrimidine synthesis?
Leflunomide
5-FU
What 2 drugs inhibit purine synthesis?
6-MP
Mycophenolate/ribavirin
What drugs inhibit both purine and pyrimidine synthesis?
Hydoxyurea
Methotrexate
Trimethoprim
Pyrimethamine
