Molecular Biology & Genetics

Front 1

Dna Methylation

Back 1

Causes DNA to coil tightly and form Heterochromatin

Front 2

Histone Acetylation or Phosphorylation

Back 2

Causes Histone Proteins to seperate from DNA and form Euchromatin.

Front 3

DNA Polymerase types

Back 3

α - Synthesise leading and Lagging Strands
δ - Synthesise leading and Lagging Strands
β - Dna Repair
ε - Dna Repair
γ - Mitochondrial DNA replication

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RNA Polymerase types

Back 4

RNA P 1 - Synthesizes all rRNA except 5s RNA
RNA P 2 - Synthesizes mRNA/hnRNA/snRNA
RNA P 3 - Synthesizes tRNA and 5s RNA

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Cytosine Deamination

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C is Replased by U in DNA

Recognized & repaired by Uracil Glycosylase & AP Endonuclease during G1 phase

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Xeroderma Pigmentosum

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Excision Endonuclease (Exinuclease) deficiency that repairs Thymine Dimers (G1) formed due to Sun light (UV) exposure

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Hereditary Non Polyposis Colorectal Cancer aka Lynch Syndrome

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hMLH1 or hMSH2 mutation leading to defective Mismatch Repair in G2 phase.
Leads to mutation accumulation in rapidly dividing intestinal cells.

Front 8

Microsatellite Instability aka Short tandem repeats

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Seen in Hereditary Non Polyposis Colorectal Cancer aka Lynch Syndrome.

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Tumor Supressor Genes

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p53
ATM
BRCA1
BRCA2
Rb

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ATM gene mutation

Back 10

Seen in Ataxia Telangiectasia characterized by hypersensitivity to X rays & predisposition to Lymphomas

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X ray Hypersensitivity

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Ataxia Telangiectasia due to ATM gene mutation.

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BRCA1 Mutation

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Breast, Prostate & Ovarian cancer

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BRCA2 Mutation

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Breast cancer

Front 14

Xeroderma Pigmentaion presentation

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Young boy with skin lesions, skin freckling, corneal ulcerations, blisters in face and neck after exposure to sunlight.

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Dyskeratosis Congenital

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Telomerase, (REVERSE TRANSCRIPTASE) deficiency

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Rifampin MOA

Back 16

Inhibits RNA Polymerase α2ββ"

Use - Tb & Prophylaxis of Meningitis (H. Infulenzae)

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Viruses that interfere with p53 & Rb gene

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Hep B & HPV

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Processing of eukaryotic Pre-Messenger RNA

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7-Methylguanosine cap
Poly A tail
Splining
Alternative splicing aka Differential splicing to produce variations of proteins

Ex B cell membrane vs secreted Ig
Tropimyocin T, I, C
Dopamine receptors in brain

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70s =

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50+30

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80s=

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60+40

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The ribosomal subunit that binds to Shine-Dalgarno Sequence in prokaryotes to initiate protein synthesis

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16s subunit of 30S

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Point Mutation Types

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Transition (A=T becomes G=C)
Transversion type (A=T becomes T=A)

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Missence Mutation

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Single Aminoacid replaced

Ex Sickle cell anemia
Glycine at 6 replaced by Valine

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Large Segment deletion mutation

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a Thalassemia & Cri Du Chat Syndrome

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Abnormal Splicing Mutation

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B Thalassemia, Gauchers, tay Sacks

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Triple Nucleotide Repeat mutations

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Huntingtons Disease (CAG - Glutamine)
Myotonic Dystrophy
Fragile X Syndrome
Friedrich's Ataxia
Spinobulbar Muscular Atrophy aka Kennedys Disease
Spinocerebellar ataxia

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Frame Shift mutation

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1 or 2 bps added or removed. Everything changes downstream

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In Frame Mutation

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3 or multiples of 3 bps are added or removed. nothing changes downstream.

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Cri Du Chat Syndrome

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Large segment deletion
Microcephaly, Mental retardation, wide set eyes & Kitten like cry

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EF2 Inhibitors aka ADP Ribosylation of EF2

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Diptheria Toxins, Pseudomonal toxins & Cycloheximide.

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Cycloheximide

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Cycloheximide is an inhibitor of protein biosynthesis in eukaryotic organisms, produced by the bacterium Streptomyces griseus

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Shiga toxin (Shygella Dysenteriae)
Verotoxin aka Shiga like toxin (enterohemorrhagic E.coli)

MAO

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Inhibit 28s of 60S ribosome

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Gray Baby Syndrome

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Chloramphenical toxicity in Babies as they do not have enough UDP glucoronyl transferase to excrete it

Blue lips, nail beds, skin,"", low bp, death.

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Abnormally Folded Protein Fate

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Ubiquitin attached & sent into Proteosome for Destruction.

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Cystic Fibrosis Etiology

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Deletion of Phenylalanine at ΔF508 which causes improper protein folding and abnormal CFTR Receptor.

Abnormal CFTR = Increased NaCl secreted in Skin & Excess NaCl absorbed form Upper respiratory Tract Secretions = Dec Cilia Movement, Dec Mucus Clearance, thick mucus and Inc infections.

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N-Terminal Hydrophobic Signal Sequence

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Present on First Exon. akes translating ribosome to stop, attach to RER & secrete protein in RER where oligosaccharides are added to protein.

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a1 Antitrypsin deficiency

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Z & S variants. Point mutation. Mutation causes protein to misfold and aggregate in ER.

presents with low serum a1 antitrypsin, Micronodular cirrhosis & fibrosis of liver

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I Cell Disease ak Mucolipidosis II

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Phosphotransferase Deficiency in ER = Nophosphorylation of mannose residues in ER.

Instead of going into Lysosomes, the enzymes are secreted into blood.

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I Cell Disease ak Mucolipidosis II Presentation

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~5 months old child with coarse facial features = Big head, Big Lips, Big tongue, Big gums (Gum Hypertrophy), saddle nose, hepatosplenomegaly, joint immobility, club foot, claw hand, scoliosis, bone fractures & deformities, Mitral Valve defects, cardiorespiratory failure & death in 1st decade

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Most unique AA in Collagen

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Hydroxyproline

Front 41

Vitamin necessary for Hydroxylation of Proline & Lysine Residues of Pro alpha chains

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Ascorbic Acid (Vit C)

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Cross Linkage of Collagen Fibrils

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Lysyl Oxidase

REQUIRES COPPER

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Type One Collagen

Distribution & Associated Disease

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Bone, Tendons, Skin

Hint 43

Osteogenesis Imperfecta
Ehlers Danlos Syndrome (Various )

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Type Two Collagen

Distribution & Associated Disease

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Cartilage (2 ears)
Vitreous Humor (2eyes)


2

Front 45

Type Three Collagen

Distribution & Associated Disease

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Everywhere

Mainly Blood vesseld and Granulation Tissue

Hint 45

Ehlers Danlos Type IV &
Keloid Scars

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Type Four Collagen

Distribution & Associated Disease

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Under the Floor

Basement Membrane

Hint 46

Alport's Disaese
Goodpastures Syndrome
Epidermolysis Bullosa

All Good Bullae

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Scurvy etiology & symptoms

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Deficient Hydroxylation of Proline secondary to Ascorbate deficiency

Hint 47

Petechiae, Echymosis, loose teeth, bleeding gums, poor wound healing, poor bone development.

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Osteogenesis Imperfecta etiology & symptoms

Back 48

mutation in collagen gene

Hint 48

BLUE SCLERA, fractures, skeletal deformities

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Ehlers Danlos syndrome etiology & symptoms

Back 49

Mutation in Collagen & Lysyl hydroxilase gene

Hint 49

Hyperextension, hypermobile joints, dislocations, varicose veins, Ecchymosis, arteria & intestinal ruptures.

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Menkes Disease aka Ehlers Danlos Syndrome Type IX aka Kinky hair syndrome etiology & symptoms

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Deficient collagen cross linking secondary to copper deficiency.

ATP7A gene mutation causing decreased absorbtion of Cu in blood.
it is absorbed in the intestinal cells but not in blood.

Hint 50

Depigmented, steely aka Kinky hair, Arterial tortuosity, rupture of arteries, cerebral degeneration, osteoporosis, anemia.

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Minkes disease presentation

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Young infant ~4 months, Abnormally kinky and hypopigmented hair. arteriogram with tortuous & elongated major arteries, bladder diverticuli, subdural hematomas,and Decreased Serum copper