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STEP Bioquimica > ADN > Flashcards

ADN Flashcards

1
Q

Acetylation in thyroid gland

A

Thyroid hormone receptors alter thyroid hormone synthesis by acetylation

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2
Q

Acetylation

A

Acetyl group added to lysine Relaxes chromatin Ups transcription

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3
Q

How do histones form Chromatin?

A

DNA loops twice around histone octamer (2x H2A, H2B, H3, H4) H1 binds to nucleosome and linker DNA condensing them into chromatin

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4
Q

Acetylation related diseases

A

Huntington: dysregulated acetylation were histone deacetylation may silence genes that should control Huntington’s protein leading to neuron cell death in striatum. Valproic acid hace effects inhibiting deacetylation

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5
Q

DNA Methylation

A

Promoted by CG islands Reduces transcription

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6
Q

Heterochromatin

A

Highly condensed NOT active for transcription Highly methylated

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6
Q

Inhibidores de síntesis de purinas

A

Azatioprina y 6 mercaptopurina Ribavirina y micofenolato

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7
Q

Euchromatin

A

Expressed DNA Less condense Histone acetylation

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8
Q

Drug induced lupus: Drugs Antibodies Symptoms

A

Drugs: hidralazine, procainamide, isoniazid

Anti-histone antibodies (95%)

Fever, joint pain, rash

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10
Q

Histone aminoacids

A

Lysine Arginine

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11
Q

Fármacos que bloquean la dihidrofolato reductasa Humanos Bacterias Hongos

A

Humanos: metrotexato Bacterias: trimetoprim Hongos: Pirimetamina

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12
Q

Fármacos que bloquean la conversión de carbamoil fosfato a ácidos orotico

A

Leflunamida bloquea la dihidroorotato deshidrogenasa inhibiendo síntesis de pirimidinas

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13
Q

Orotic Aciduria Enzyme deficiency Clinical findings Treatment

A

Defect in UMP synthase Buildup of orotic acid + loss of pyrimidines Autosomal recessive Orotic acid in urine + megaloblastic anemia + hypersegmented neutrophils with NO response to B12 or B9 + Growth retardation Treatment: Uridine —> Bypasses UMP synthase

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14
Q

Differential diagnosis for orotic aciduria

A

Orhithine transcarbamylase (OTC) deficiency Enzyme combines carbamoyl phosphate + ornithine to make citrulline in urea cycle Causes orotic aciduria however it also has high levels of ammonia and generates encephalopathy (baby with lethargy and coma)

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15
Q

Drug that inhibit dUMP to dMTP + enzyme

A

Enzyme: Thymidylate synthase Drug: 5-fluorouracil (5-FU)

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16
Q

Pyrimidine analog that mimics dCTP

A

Cytarabine: chemotherapy agent that inhibits DNA polymerase

17
Q

Trimethoprim Sulfa action mechanism

A

Inhibits formation of thymidine (dTMP)

  • Sulfonamide mimics PABA
  • Trimethoprim inhibits dihydrofolate reductase
18
Q

Folate trap

A
19
Q

Folate vs B12 deficiency anemia

A
  • Both are macrocytic anemias with hypersegmented neutrophils
  • Both are caused by defective DNA synthesis –> Thymidine synthesis
  • Both have high homocysteine levels
  • Only B12 has high methymalonic acid levels
20
Q

Purine precursors

A
  • N: GAG –> glycine, glutamine, aspartato
  • C: CO2, Tetrahidrofolato
  • 5 ribose phosphate
21
Q

Pyrimidines precursors

A
  • N: glutamine and aspartate
  • C: tetrahydrofolate and CP2
  • ribose phospate
22
Q

DNA Damage

A
23
Q

DNA Repair Mechanisms

A

Single strand:

  • Base excision: Recognise específico base errors ( deamination, oxidation, open rings)
  • Nucleotide excision: Damage in multiple bases generated by UV radiation. Only G1.
  • Mismatch repair: Damage in DNA match between strands. Backup if proofreading misses error. Only S and G2. Related to microsatelite stability.

Double Strand: Radiation

  • Hologous end joining: Uses sister chromosome template.
  • Non-homologous end joining: No template so it is highly prone to error.
24
Q

Illness related to defects in DNA Repair

A
  • Xeroderma pigmentosaum: nucleotide excision repair
  • Lynch syndrome: mismatch repair. Microsatelite inestabilidad. Mutations in MLH1 and MSH2. Colon, endometrium, ovarian and skin cancer.
  • Franconia anemia: homologous end joining. Mutation in DNA repair enzymes causes cells vulnerable to DNA cross links.
    Ataxia telangiectasia: non-homologous end joining repair. 4 A’s.

STEP Bioquimica (1 decks)

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