Molecular Flashcards
What are the purines?
- Adenine
- Guanine
What are the pyrimidines?
- Cytosine
- Thymine
- Uracil
How many times does DNA loop around histone?
Twice
What does H1 act as?
A histone linker
During what phase does DNA and histone synthesis occur?
S phase
What are Barr Bodies?
Inactive X chromosomes
What gives DNA a negative charge?
Phosphate
What amino acids give histones a positive charge?
- Lysine
- Arginine
What does histone acetylation do?
- Increases transcription
- Removes histone’s positive charge, relaxing coiling
- Attaches to lysine
What sequence of genes represses transcription?
CpG islands (C, G) - Methyl group attaches to Cytosine
What processes involve DNA methylation?
- Aging
- X chromosome inactivation (lyonization)
- Carcinogenesis
- Genomic imprinting
- Transposable element repression
What disease is thought to be due to dysregulated acetylation?
Huntington’s
What do nucleosides lack?
A phosphate group
How many rings do purines (A, G) contain?
2
How many rings do pyrimidines (CUT) contain?
1
How many H bonds do the bases have?
- C-G bond has 3 (higher melting point)
- A-T bond has 2
What does deaminated Cytosine become?
Uracil
What does deaminated Adenine become?
Hypoxanthine
What does deaminated Guanine become?
Xanthine
What does deaminated 5-methylcytosine become?
Thymine
What does methylation of uracil make?
Thymine
What amino acids are necessary for purine synthesis?
- Glycine
- Aspartate
- Glutamine
What makes up a nucleoside and a nucleotide?
- Nucleoside = base + sugar (ribose/deoxyribose)
- Nucleotide = base + sugar + phosphate
Why does the C-G bond have a higher melting point than the A-T bond?
C-G has 3 Hydrogen bonds whereas A-T has 2
What do antibodies target in drug-induced lupus?
Histones (in >95% of cases)
What drugs are responsible in drug-induced lupus?
- Hydralazine (BP and HF drug, vasodilator)
- Procainamide (ant-arrhythmic)
- Isoniazid (anti-TB)
HIP
What is the source of Nitrogen in humans?
Amino acids (usually meats/protein rich foods)
What kind of molecule is DNA?
Polymer (made up of individual nucleotides [monomers])
The Nucleosides are called:
Pyrimidines: (-idine)
Cytidine, Uridine, Thymidine
Purines: (-sine)
Adenosine, Guanosine
The bases are called:
Pyrimidines:
Cytosine, Uracil, Thymine
Purines:
Adenine, Guanine
How many phosphate groups do the nucleotides have when incorporated into DNA?
3 (triphosphate form)
- They are synthesised as monophosphates then converted to triphosphates
- The 2 phosphates are cleaved off once the nucleotide is attached
- E.g Deoxyadenosine Triphosphate
What can unmethylated CG islands cause?
Immune response
What is the purpose of methylation in bacteria?
Protection from bacteriophages
- They can methylate both A and C
What do the antibodies target in classic lupus?
The dsDNA molecules (drug induced it id the histones)
What substances are required to make Purines (A, G)?
- Glycine (2C, 1N)
- Aspartate (1N)
- Glutamine (2N)
- 2x N10-Fomyl-tetrahydrofolates (2C)
- CO2 (1C)
What substances are required to make up pyramidines (C, U, T)?
- Aspartate (3C, 1N)
- Carbamoyl phosphate (1N, 1C)
