Biochemistry Flashcards
What is the only histone that is not located in the nucleosome core?
H1
what is the form of chromatin that is transcriptionally active?
Euchromatin
What are the purine nucleotides?
What are the pyrimidine nucleotides?
Purines - A, G
Pyrimidines - C, U, T
How can you make uracil from cytosine?
Deamination of cytosine makes uracil
What are the amino aids necessary fro purine synthesis?
GAG
Glycine
Aspartate
Glutamine
you also need tetrahydrofolate
what is the rate limiting enzyme in pyrimidine base production?
Carbamoyl phosphate synthetase II
What enzyme does Hydroxyurea block that’s used in the synthesis of pyrimidines?
Hydroxyurea blocks ribonucleotide reductase
Used to treat sickle cell disease and cancer
What enzyme does 5-FU block that’s used in the synthesis of pyrimidines?
Thymidylate synthase is blocked therefore you can’t make dTMP
What enzyme does MTX/TMP block that’s used in the synthesis of pyrimidines?
Dihydrofolate reductase is blocked therefore you can’t make dTMP
What enzyme does 6-MP block that’s used in the synthesis of purines?
6-MP inhibits glutamine PRPP Amidotransferase
Note that this is the rate limiting enzyme in purine synthesis
What enzyme does Mycophenolate block that’s used in the synthesis of purines?
Mycophenolate blocks IMP dehydrogenase so you can’t make GMP
Autosomal recessive disease where you are unable to convert orotic acid to UMP because of defect in UMP synthase
Orotic aciduria
effects de novo pyrimidine synthesis pathway
Patient presents with megaloblastic anemia that does NOT improve with administration of vitamin B12 or folic acid, failure to thrive and they do NOT have hyperammonemia. The patient has increased orotic acid in the urine
Orotic aciduria
What is the treatment for orotic aciduria
Oral uridine administration
What two drugs inhibit xanthine oxidase?
Allopurinol and Febuxostat
What immunosuppressants do you need to decrease when you are also giving a patient allopurinol or febuxostat?
Azathioprine and 6-MP
What is the triad seen in SCID?
- severe recurrent infections
- chronic diarrhea
- failure to thrive
Excess ATP and dATP imbalances nucleotide pool via feedback inhibition of ribonucleotide reductase therefore preventing DNA synthesis and therefore decreasing lymphocyte count
Adenosine deaminase deficiency
leads to SCID, AR disease
Patient presents with excess uric acid production and de novo purine synthesis. They have a defective purine salvage pathway because they do not have HGPRT
Lesch nyhan syndrome
HGPRT converts hypoxanthing to IMP
A patient is found with retardation, self-mutilation, aggression, hyperuricemia, gout, and choreoathetosis
Lesch-Nyhan syndrome
What can you use to treat lesch-nyhan syndrome?
Allopurinol, but note that this will not help with CNS problems
a point mutation in DNA where it results in the same amino acid, often the third base has changed (tRNA wobble)
Silent mutation
A point mutation where there has been a change in the amino acid but it’s conservative because the new amino acid is similar in chemical structure but the result is a polypeptide product that has different structural or functional properties
missense mutation
Ex - sickle cell
A point mutation that results in an early stop codon
Nonsense mutation
A point mutation that results in misreading of all nucleotides downstream, often resulting in a truncated, nonfunctional protein
Frameshift mutation
What autoantibody is made against topoisomerase?
anti-Scl-70
seen in diffuse scleroderma
mutation in nucleotide excision repaid resulting in lack of repair of pyrimidine dimers due to UV light exposure
————children of the night
Xeroderma Pigmentosum (AR)
what is the repair mechanism where newly synthesized strand is recognized and mismatched nucleotides (like a T with a G) are removed and gap is filled and resealed?
Mismatch Repair
In what cancer is mismatch repair mutated?
hereditary nonpolyposis colorectal cancer
a patient presents with decreased IgA, cerebellar ataxia, poor smooth pursuit of the eyes and they are sensitive to ionizing radiation. the patient has a mutated nonhomologous end joining
Ataxia telangiectasia
What is the mRNA start codon?
AUG
methionine in eukaryotes
formylmethionine (f-met) in prokaryotes
What are the 3 mRNA stop codons?
UGA
UAA
UAG
how many RNA polymerases do prokaryotes have and what do they do?
Prokaryotes have 1 RNA polymerase that makes rRNA, mRNA and tRNA
What antibiotic inhibits prokaryote RNA polymerase?
Rifampin
What are the RNA polymerases used in eukaryotes and what do they make?
RNA polymerase 1 - makes rRNA
2- makes mRNA
3- makes tRNA
a patient eats a amanita phalloides death cap mushroom and gets severe hepatotoxicity. What is the toxin and what is it inhibiting?
Alpha amanitin is the toxin and it inhibits RNA polymerase II
Where does RNA processing occur and what are the 3 stages of RNA processing?
Occurs in the nucleus
- capping on 5’ end (addition of 7-methylguanosine cap via SAM)
- polyadenylation on 3’ end, signal is AAuAAA
- splicing out introns
what sequence sits at the 3’ end of tRNA?
CCA
what antibiotic binds to the 30S subunit preventing attachment of aminoacyl-tRNA from entering the acceptor site?
Tetracyclines
what enzyme is responsible for adding an amino acid to the tRNA?
aminoacyl-tRNA synthetase
What antibiotics bind to 30S and inhibit formation of initiation complex and causes misreading of mRNA
Aminoglycosides
What antibiotics binds the 50s subunit and inhibits peptidyl transferase? (23s rRNA)
Chloramphenicol
what antibiotics bind to the 50s subunit and prevent release of uncharged tRNA after it has donated its amino acid, thereby preventing the translocation step?
Macrolides
what tumor suppressors prevent the G1 to S phase progression?
Rb and p53
What are the Cyclin/CDK involved in G1 to S phase?
Cyclin D with CDK4 and Cyclin E with CDK2
What are the cyclin/CDK involved in the G2 to M phase?
Cyclin A with CDK2 and Cyclin B with CDK1
what are the functions of smooth ER?
- steroid synthesis
2. detoxification of drugs and poisons
What is responsible for synthesizing enzymes like ChAT and peptide neurotransmitters in neurons?
Nissl bodies or RER found only in dendrites
What must be added to a protein in order for it to go to the lysosome?
Mannose-6-phosphate
A patient is deficient in a phosphotransferase and is unable to add mannose-6-phosphate to proteins. what is the disease and what’s the result?
The patient has I cell disease
This results in enzymes being secreted outside the cell instead of being targeted to the lysosome
A patient presents with coarse facial features, clouded corneas, restricted joint movement and high plasma levels of lysosomal enzymes. what is this?
I cell disease
often fatal in childhood
Name 5 drugs that act on microtubules
- Mebendazole
- Griseofulvin
- Vincristine/Vinblastine
- Paclitaxel
- Colchicine
What are the two molecular motor proteins that transport cellular cargo toward opposite ends of microtubule tracts?
Dynein - retrograde to microtubule (+ –> -)
Kinesin - anterograde to microtubule (- –> +)
a patient presents with recurrent pyrogenic infections, partial albinism, and peripheral neuropathy. What is the syndrome and what is mutated?
Chediak higashi syndrome
Mutated lysosomal trafficking regulator gene (LYST)
A patient presents with decreased fertility, bronchiectasis, and recurrent sinusitis what is the syndrome and what is the defect?
The patient has Kartagener’s syndrome (primary ciliary dyskinesia)
They have immotile cilia due to a dynein arm defect - associated with situs inversus
What cell type is seen with a vimentin stain?
Connective tissue
Sarcomas
What cell type is seen with a desmin stain?
Muscle
rhabdo or leiomyoscaroma
What cell type is seen with a cytokeratin stain
Epithelial cells
Carcinoma
What cell type is seen with a GFAP stain?
Neurogluia
Astrocytoma, glioblastoma
What cell type is seen with a neurofilament stain?
Neurons
Neuroblastoma, primitive neuroectodermal tumor
what drug inhibits the Na/K ATPase pump by binding to the K+ site?
Ouabain
What is the mnemonic to remember collagen types 1 - 4?
Strong (1), Slippery (2), Bloody (3), Bowel Movement (4)
Where is type 1 collagen found
bone, skin, tendon, dentin, fascia, cornea, late wound repair
Where is type 2 collagen found
Cartilage (including hyaline), vitreous body, nucleus pulposus
where is type 3 collagen found
Reticulin - skin, blood vessels, uterus, fetal tissue, granulation tissue
where is type 4 collagen found
Basement membrane or basal lamina
A patient is deficient in vitamin C and they are DX with scurvy, what exactly can they not do?
the step of collagen synthesis with hydroxylation of specific proline and lysine residues
if a patient can’t form a triple helix during the glycosylation step of collagen synthesis, what disorder do they most likely have?
Osteogenesis imperfecta
If a patient is unable to perform the cross linking step in collagen synthesis to make collagen fibrils, what disorder do they most likely have?
Ehlers danlos
A patient presents with multiple fractures with minimal trauma, blue sclerae (transluscent CT over the choroidal veins), hearing loss and dental imperfections (lack of dentin). What is the name of the disorder and the defect
Osteogenesis imperfecta. Defect in type 1 collagen. the most common form is AD and is due to decreased production of otherwise normal type 1 collagen
A patient presents with hyperextensible skin, tendency to bleed and hypermobile joints
Type 1 or 5 collagen most frequently
Ehlers danlos
A patient presents with hematuria, oliguria, high frequency hearing loss - what’s wrong with him?
Alport syndrome
Defect in Type 4 collagen - basement membranes
a patient presents with hyperelastic joints, problems wit heart vales, aorta, very tall, arachnodactyly, pectus carinatum and Steinberg sign. What is the syndrome and defect?
Marfan syndrome - fibrillin defect
Why do we get wrinkly?
reduced collagen and elastin production
What is the blotting procedure where you use a known DNA probe to ID a DNA sample?
Southern blotting
What is the blotting procedure where you use a known DNA probe with an RNA sample. This is useful for studying mRNA levels
Northern blot
What is the blotting procedure where you use an Ab probe to look at a protein sample
Western blot
What is the blotting procedure where you use a labeled oligonucleotide probe to look at DNA binding proteins like transcription factors
Southwestern blot
What type of ELISA uses a test antigen to see if a specific antibody is present in a person’s blood?
Indirect ELISA
What type of ELISA uses a test antibody to see if a specific antigen is in a patients blood?
Direct ELISA
What technique should you use is you want to look for specific localization of genes and direct visualization of anomalies at the molecular level?
FISH
What is the genetic term where the phenotype varies among individuals with the same genotype. Example: 2 patients with neurofibromatosis type 1 may have varying disease severity.
Variable expressivity
What is the genetic term where not all individuals with a mutant genotype shows the mutant phenotype. Example: may skip a generation, BRCA1 gene mutation doesn’t always result in breast or ovarian cancer?
Incomplete penetrance
what is the genetic term where one gene contributes to multiple phenotypic effects? Example: PKU causes many seeminly unrelated symptoms ranging from mental retardation to hair/skin changes
Pleiotropy
What is the genetic term where differences in gene expression depend on whether the allele is of maternal or paternal origin
Imprinting
What is the genetic term where there is increased severity or earlier onset of disease in succeeding generations?
Anticipation
What is the genetic term where if a patient inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops. This is NOT true of oncogenes.
Loss of heterozygosity
“two hit hypothesis”
What is the genetic term that exerts a dominant effect where a heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning. Example: mutation of a transcription factor in its allosteric site. Nonfunctioning mutant can still bind DNA, preventing wild type transcription factor from binding.
Dominant negative mutation
What is the genetic term where there’s a tendency for certain alleles at 2 linked loci to occur together more often than expected by chance. Measured in a population, not in a family, and often varies in different populations?
Linkage disequilibrium
What is the genetic term that occurs when cells in the body differ in genetic makeup due to postfertilization loss or change of genetic information during mitosis.
Mosaicism
What is the genetic term where mutations at different loci can produce the same phenotype? Examples include how mafran’s syndrome, MEN 2B, and homocystinuria all cause marfanoid habitus. or all the different things that can cause albinism
Locus heterogeneity
What is the genetic term where there’s the presence of both normal and mutated mitochondrial DNA, resulting in variable expression in mitochondrial inherited disease?
Heteroplasmy
A patient presents with mental retardation, hyperphagia, obesity, hypogonadism and hypotonia. They also have a chromosome 15 problem where the mom gene is inactivated and the dad gene is deleted.
Prader-willi syndrome
A patient presents with mental retardation, seizures, ataxia, and inappropriate laugher. They also have a chromosome 15 problem where the dad gene is inactivated and the mom gene is deleted
Angelman’s syndrome
A patient presents with dwarfism, short limbs, larger head, but trunk size is normal. They have a super old dad. Whats the disorder, the inheritance pattern and the defect?
Achondroplasia, AD, defect of fibroblast growth factor receptor 3
a patient presents with a colon covered with adenomatous polyps after puberty. What is the disease, inheritance pattern and the defect?
Familial adenomatous polyposis. This is due to a mutation on chromosome 5, APC gene
The concern is that it progresses to colon cancer unless colon is resected
a patient presents with bilateral massive enlarged kidneys. They have flank pain, hematuria, hypertension, and progressive renal failure. What is the disease, inheritance pattern and the defect?
Autosomal dominant polycystic kidney disease
The defect is on chromosome 16, PKD1 gene
A patient presents with elevated LDL due to defective or absent LDL receptor. They have severe atherosclerotic disease early in life, tendon xanthomas and they may have an MI very early in life. What is the disease, inheritance pattern and the defect?
Familial hypercholesterolemia (Hyperlipidemia type IIA) Autosomal dominant
A patient presents with telangiectasia, recurrent epistaxis, skin discolorations and arteriovenous malformations. What is the disease, inheritance pattern and the defect?
This is Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) - AD
This is a inherited disorder of blood vessels
A patient presents with hemolytic anemia, increased MCHC, increased viscosity in blood, jaundice, worsened with viral infections and abnormal osmotic fragility test. What is the disease, inheritance pattern and the defect?
Hereditary spherocytosis. AD. This is spheroid erythrocytes due to a spectrin or ankyrin defect.
A patient presents with depression, progressive dementia, choreiform movements, caudate atrophy, and decreased levels of GABA and ACh in the brain. What is the disease, inheritance pattern and the defect?
This is Huntington’s disease (AD), gene located on chromosome 4 it is a trinucleotide repeat (CAG)
A patient presents with café-au-lait spots, neural tumors, lisch nodules (pigmented iris hamartomas), scoliosis and optic pathway gliomas. What is the disease, inheritance pattern and the defect?
This is neurofibromatosis type 1 (von Recklinghausen’s disease) AD. defect on long arm of chromosome 17
A patient presents with tinnitus, balance problems, hearing loss due to bilateral acoustic schwannoma and juvenile cataracts. What is the disease, inheritance pattern and the defect?
This is neurofibromatosis type 2. AD
NF2 gene on chromosome 22
A patient presents with seizures, intellectual disability, and angiofibromas. they also have ash leaf spots on skin, renal cysts and renal angiomyolipomas. What is the disease, inheritance pattern and the defect?
Tuberous sclerosis - AD, mutated hamartin (tuberin) gene
shwos incomplete penetrance and variable persentation
A patient presents with hemangioblastomas or retina/cerebellum/medulla, the majority of affected individuals also develop multiple bilateral renal cell carcinomas and other tumors. What is the disease, inheritance pattern and the defect?
This is von Hippel-Lindau disease, AD. deletion of VHL gene (tumor suppressor) on chromosome 3.
results in constitutive expression of HIF (transcription factor) and activation of angiogenic growth factors
what deletion is seen in cystic fibrosis?
CFTR gene is deleted on chromosome 7, commonly a deletion of Phe 508
this is AR
A patient presents with recurrent pulmonary infections, chronic bronchitis, bronchiectasis, pancreatic insufficiency, nasal polyps and meconium ileus as a newborn. What is wrong with them?
Cystic fibrosis
What is the inheritance and the mutation seen in Duchenne’s muscular dystrophy?
X-linked frameshift mutation, deletion of dystrophin gene
onset before age 5 yo
How do you diagnose muscular dystrophies?
Muscle biopsy and increased CPK
as the disease progresses the CPK will decreased due to inactivity and muscle loss
what is the less severe form of duchennes muscular dystrophy?
Becker’s
This is a X-linked mutated dystrophin gene
A patient presents with marcoorchidism, long face with a large jaw, large everted ears, autism, mitral valve prolapse and mental retardation.
Fragile X syndrome
X linked. CGG repeat - FMR1 gene
What is the trinucleotide repeat seen in Friedreich’s ataxia?
GAA
What is the trinucleotide repeat seen in myotonic dystrophy?
CTG - autosomal dominant