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GER Unit 1 > MCP 1 > Flashcards

MCP 1 Flashcards

1
Q

what is biochemical genetics

A

genetic branch that deals with inborn errors of metabolism which are single enzyme defects that produce a metabolic block by accumulation of substrate and/or deficiency of products
e.g., PKU

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2
Q

Phenylketonuria (PKU)

A

defect of PAH enzyme; no phenylalanine–>tyrosine, accumulation of phenylalanine can be fatal; treat with restrictive diet

  • Varient PKU: moderate severity
  • Non-PKU: least severe
  • *example of phenotypic heterogeneity: 3 distinct phenotypes from single gene mutation
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3
Q

Tetrahydrobiopterin (BH4)

A

defect of cofactor for conversion of phenylalanine–>tyrosine
**example of locus heterogeneity: same clinical phenotype as PKU but mutation in a different gene

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4
Q

major differences between spermatogenesis and oogenesis

A
  • continual production of 1˚ spermatocytes vs. all present at birth
  • continual production of spermatids vs. monthly
  • 1˚ sperm. produces 4 spermatids vs. 1˚ oocyte produces 1 ovum
  • completes meiosis II vs. not complete until fertilization (stays in mid meiosis I until ovulation then goes to metaphase II; ovum not created until fertilization)
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5
Q

what is the reduction division and when does it take place?

A

reduction in number of chromosomes from 2N–>N when centromeres divide

  • occurs at anaphase I
  • potential for nondisjunction
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6
Q

Down Syndrome

A

trisomy 21; most common form of mental retardation, level of severity based on when nondisjunction event occurs

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7
Q

Patau Syndrome

A

trisomy 13; punched in head, polydactyly

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8
Q

Edwards Syndrome

A

trisomy 18; specific hand sign

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9
Q

Lyon hypothesis

A
  • x inactivation in all female somatic cells (or anytime there are two x chromosomes)
  • inactive x condensed into barr body (epigenetic modification)
  • reactivated during female meiosis; gametes must be XX
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10
Q

Hereditary non-polyposis colon cancer

A

-defect of mismatch repair pathway; causes mutator phenotype and thus accumulates DNA mutations more rapidly than normal

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11
Q

Ataxia telangiectasia

A

mutation in ATM gene that codes for protein important in replication stress response (which halts replication if DNA is damaged or there is a nucleotide shortage)

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12
Q

Bloom syndrome

A

mutation in BLM gene that codes for protein important in replication stress response (which halts replication if DNA is damaged or there is a nucleotide shortage)

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13
Q

Xeroderma pigmentosum

A

consequence of unrepaired DNA damage; inability to repair ace damage resulting from UV exposure increases mutational burden in cells and eventually neoplastic transformation

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14
Q

what are the ways in which medications can permeate cell membranes?

A
  • hydrophobicity (passive diffusion)
  • hijack transporters (make it look like something normally transported)
  • package in lyposome
  • protein transduction (sequences interact directly with membrane)
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15
Q

Kleinfelter syndrome

A

XXY; males with broad phenotypic expression (tall, man boobs); usually infertile

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16
Q

Turner Syndrome

A

result of a rare nondisjunction error

  • 45, X; females with short stature, neck webbing, usually infertile
  • 45, X/46, XY mosaicism may have male or female phenotype (male=normal, female=turner with increased risk of gonadoblastoma)
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17
Q

Androgen Insensitivity

A

XY female: mutation of androgen receptor gene located on long arm of X, TDF initiates male development but pathway blocked; infertile due to nonfunctional genitalia

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18
Q

Congenital adrenal hyperplasia

A

XX “male”; autosomal recessive, mutation results in overproduction if androgens in female fetus (androgens can cross placenta)

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19
Q

Wolf-Hirschorn Syndrome

A

4p-; chromosome deletion, phenotype displays in Greek warrior helmet head, risk of seizure, and need for specialEd

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20
Q

What is Tm and what affects it?

A

temperature at which 1/2 of DNA has melted

  • size matters (bigger, the higher the Tm)
  • high G+C content = high Tm
  • high salt = high Tm
  • high [OH] = low Tm (inversely proportional to pH)
  • formation of H-bonds with bases stabilize single-stranded DNA and decrease Tm
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21
Q

30nm chromatin fiber

A

DNA coiled around 8 positively charged histones (H2A, H2B, H3, H4 x2); attaches to H1

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22
Q

Explain the mechanism of import through NPC

A

protein with nuclear localization signal bound to importin (directs docking on NPC); complex translocated to the nucleus; RanGTP (GEF catalyzed GDP–>GTP) binds importin, cargo released. RanGTP-importin complex diffuse to cytoplasm, RanGAP hydrolyzes GTP–>GDP and importin is recycled

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23
Q

Explain the mechanism of export through NPC

A

RanGTP, exportin and cargo are translocated to the cytoplasm; hydrolysis of GTP–>GDP by RanGAP causes complex to dissociate, export cargo is released.

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24
Q

nucleolus

A

primary function is ribosome biogenesis;

  • granular component: maturing ribosomal particles
  • dense fibrillar: active ribosomal synthesis
  • fibrillar center: no active synthesis
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25
Q

microfilaments

A
  • globular actin
  • dynamic, important for cell shape
  • structural polarity; uses myosin (towards +end)
  • treadmilling (monitored by thymosins and profiling): ATP bound actin assembles into filament, assembled subunits hydrolyze ATP, ADP-actin dissembles (at - end) and free subunits exchange nucleotide over time
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26
Q

list actin-associated membrane structures

A
  • microvilli
  • lamellipodia; branched filaments, assemble on ARP complexes until the ends until capped,
  • contractile ring in dividing cell
  • stress fibers
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27
Q

describe the regulation of skeletal muscle contraction

A
  • attached: short-lived rigor, myosin lacks ATP and is tightly bound to actin
  • released: normal relaxed state, ATP bound and myosin not attached to actin
  • cocked: ATP hydrolysis causes translocation of head to cock it in preparation for power stroke, weak actin affinity
  • force-generating: dissociation of Pi increases affinity of myosin for actin, activates power stroke
  • attached: dissociation of ADP by translocation of myosin head back to original configuration
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28
Q

robertsonian translocation

A

centromere to centromere translocation involving acrocentric chromosomes; results in loss of both short arms; normal offspring but only 45 true chromosomes

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29
Q

paracentric translocation

A

break on same side of centromere; inversion loop to pair properly; arm ratio unchanged, no problem unless recombination within the loop (no viability, apparent suppression of recombination)

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30
Q

pericentric translocation

A

break on opposite side of centromere; inversion loop to pair properly; results in duplication and deletion of genes (changes arm ratio); larger the inversion, the more viable the gametes

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31
Q

intermediate filaments

A

no structural polarity, high tensile strength, assemble into rope like filaments

  • keratins: epithelia, mutation causes skin blister disease
  • vimentin: mesoderm; connective tissue, muscle cells, and glial cells
  • neurofilament proteins: nerve cells
  • nuclear lamins: inner surface of inner nuclear membrane; mutation causes progeria
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32
Q

microtubules

A
  • a and ß tubulin heterodimer
  • associate with dyneins and kinesins
  • dynamic instability
  • stabilized by MT-associated proteins in nerve
  • gamma tubulin: triplet MTs that form centrosomes
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33
Q

describe dynamic instability

A

allows MT array to search cytoplasm for structure to which to attach

  • GTP bound assemble, ß can hydrolyze GTP to GDP; if assembly faster than hydrolysis, MT grows
  • maturation: no more dynamic instability
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34
Q

roles of dynein and kinesin as MT motors for MTs

A

dynein to -end; kinesin to +end

ex. neuron: outward = kinesin (e.g. neurotransmitters), inward = dynein (e.g., recycled membrane, neurotropic viruses)
ex. non neural cell: kinesin stretch ER from nucleus, dynein keeps golgi near nucleus

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35
Q

Kartageners Syndrome

A

lack of motility in what should normally be motile cilia, results in respiratory diseases, infertility in males, heterodoxy

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36
Q

Polycystic Kidney Disease

A

mutation in protein needed for assembly of nonmotile cilia, results in abnormal growth regulation of epithelial cells and formation of cysts

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37
Q

describe protein import into mitochondria

A

powered by ATP hydrolysis and electrochemical gradient across inner membrane; TOM receives mitochondrial sorting signal, lateral diffusion until TIM encounter, translocated through Tom and then TIM; hsp70 translocate protein in unfolded state, signal peptidase cleaves sorting signal, hsp60 folds protein

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38
Q

peroxisome

A
  • oxidative degradation with catalase
  • beta oxidation
  • synthesis of cholesterol, bile acids, lipids
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39
Q

Zellweger Syndrome

A

problem importing enzymes into peroxisome, severe defects and early death

40
Q

X-linked adrenoleukodystrophy (ALD)

A

lack membrane protein for long chain fatty acid degradation, leads to demyelination of neurons; lethal without stem cell transplant
-HIV derived lentiviral vector for gene therapy

41
Q

describe the process of cotranslation transport from cytosol to the ER

A
  • signal recognition particle slows translation process so there is time to interact with ER membrane
  • binds with SRP receptor, synthesis through the membrane, signal peptidase cleaves signal sequence
  • released into lumen for golgi sorting unless hydrophobic stop-transfer sequence is present
42
Q

smooth ER functions

A
  • synthesis of steroid hormones
  • detoxification of lipid soluble drugs
  • protein modifications (N-linked co-translationally)
  • quality control by chaperones; unfolded protein response up regulates chaperones/hsps as needed
43
Q

golgi functions

A
  • protein sorting

- processing to create glycoproteins and proteoglycans (O-linked by glycosyltransferases)

44
Q

glycoproteins

A
  • mostly protein, little carb
  • N-linked: blocks of sugars added as a whole (in ER)
  • O-linked: build one sugar at a time (ex. mucins, ABO blood group antigens) by glycosyltransferases (in golgi)
45
Q

proteoglycans

A
  • mostly carb with a little protein

- highly negatively charged because of carboxyl and sulfate groups, forms lubricants and gels

46
Q

LDL receptor

A

types of constitutive pinocytosis (receptor mediated endocytosis); mediates the endocytosis of LDL, associate with clathrin coated pits and internalized with bound LDL; vesicles fuse with early endosomes; LDL dissociates in lysosome where it is hydrolyzed to free cholesterol

47
Q

macrophage

A

type of phagocytic cell that phagocytoses red blood cells

48
Q

transcytosis

A

typically occurs in a polarized cell, ex. lactating women: antibodies in blood are taken up by epithelial cells and sorted into early endosome and set from apical surface into breastmilk

49
Q

endocrine signaling

A

signals are carried through blood stream, highest affinity receptors

50
Q

synaptic signaling

A

signals have very small location to traverse, lowest affinity receptors

51
Q

primary signal transduction

A

mechanism by which nuclear receptors regulate gene expression; ligand (hormone) binds to receptor, DNA-binding portion within nucleus is exposed and receptor can bind to all genes with matching promoter sequence

52
Q

types of transmembrane surface receptors

A
  • ion-channel linked
  • GPCRs
  • Enzyme-linked
53
Q

adenylyl cyclase pathway

A

Gs binds and activates adenylyl cyclase, catalyzes conversion of ATP into cAMP, cAMP diffusions through cytoplasm and activates PKA which can then phosphorylate other proteins; Gi inhibits cAMP production

54
Q

Gq

A

activates PLC which generates IP3 and DAG; –DAG: second messenger that activates PKC
-IP3: binds gated channels in ER to release Ca 2+

55
Q

Calmodulin

A

protein that changes conformation dramatically when Ca 2+ ions bind to its 4 Ca binding sites; Ca 2+ calmodulin activates MLCK which phosphorylates myosin light chain kinase; enables myosin cross bridge to bind actin filament and allow for muscle contraction

56
Q

receptor tyrosine kinases

A

dimerize to phosphorylate itself (no conformational change); common receptors for growth factors (choices between cell division and differentiation)
ex. SH2 domain binds/activates Ras, Ras with GTP bound activates MAP kinase cascade, MAPkkk–> MAPkk–> MAPk–> increases cyclin gene transcription and inactivates inhibitor proteins (increase [CDK] activity = passage into cell cycle)

57
Q

adhering/anchoring junctions

A

maintain tissue integrity

  • adherens: cell-cell, cadherins, actin
  • focal adhesions: cell-ECM, integrins, actin
  • desmosome: cell-cell, cadherins, IF
  • hemi-desmosome: cell-ECM of basal lamina, integrins, IF
58
Q

tight junctions

A

permeability barrier across epithelial sheets; maintains polarity; claudin and occluding;

59
Q

gap junctions

A

connexon pores provide communication between neighboring cells; ex. electrical conduction in cardiac muscle; regulated by solute concentration, pH, phosphorylization

60
Q

fibrous proteins

A
  • collagen: tensile strength, ehlers danlos syndrome; pro peptide cleavage allows for higher order structures
  • elastin: elasticity, proline, resists stretching, mar fans syndrome
  • keratins
61
Q

allelic heterogeneity

A

different mutations at the same locus cause same disease (ex. different mutations in the β-globin gene = thalassemia)

62
Q

locus heterogeneity

A

mutations at different locus cause same disease (ex. autosomal dominant, autosomal recessive, and X-linked origins but only 1 mutant locus = retinitis pigmentosa)

63
Q

clinical heterogeneity

A

same gene mutations cause different disease phenotypes

64
Q

haldane’s rule

A

applies to x-linked recessive with no maternal family history other than one affected boy with reduced fitness; exception: fragile x
2/3 carrier status of parent and 1/3 carrier status of sibling

65
Q

chimera

A

blending of 2 different zygotes; in germ line then genetically, children are niece and nephews

66
Q

4 stages of cell cycle

A
  • G1: gap before DNA synthesis, most cells
  • S: DNA replication, histone synthesis
  • G2: gap after DNA synthesis; addition of cohesins to link sister chromatids and condensins to condense chromosomes
  • M: centrosome duplication and mitosis
67
Q

mitosis

A
  • prophase: chromosomes condense, spindle forms, nuclear envelope break down signals prometaphase (chromosomes attach to spindle MTs)
  • metaphase: alignment at metaphase plate; tension on kinetochores activates anaphase promoting complex
  • anaphase: chromosomes move closer to poles and further from each other
  • telophase: cytokenesis; spindle disassembly/ nuclear reassembly;
68
Q

cyclin dependent kinase

A

CDKs regulate major cell checkpoints; gradual increase in [cyclin] reflects continuous protein synthesis; turned off by ubiquitylation by E3 ubiquitin ligase
-G1/S: start
G2/M: enter M
Metaphase/Anaphase: exit M

69
Q

p53

A

stabilizes CDK protein against proteolytic degradation; binds DNA and activates expression of p21 gene; p21 protein binds molecules important for the G1/S transition in the cell cycle; mutant p53 means no available p21 to act as the “stop signal” for cell division

70
Q

internal controls of G1/S progression

A
  • apoptosis: programmed cell death, cyc c–> caspase cascade
  • terminal differential: cell only expresses genes specific to cell type and function; nonreversible
  • senescence: cells in culture stop devising after 50-100 divisions due to absence of telomerase
71
Q

external controls of G1/S progression

A
  • growth factors: concentration and cell-type specific; local (PDGF wound repair) and systemic (ex. erythropoetin)
  • cell-ECM interactions (stimulate)
  • cell-cell inhibit
72
Q

oncogenes

A

disregulated (mutated or over expressed) version of genes normally found in cellular genome (protooncogenes); just need a single allele to give rise to abnormal growth, not usually inherited

73
Q

tumor supressor genes

A

act antagonistically with protocongoenes to inhibit growth; both alleles must be mutated or deleted, often inherited (predisposition for cancer)
ex. p53

74
Q

DNA viruses

A

ex. HPV; carries genes in their normal genome that encode proteins that block Rb and p53 function; leads to hyperproliferation/ transformation of infected cell

75
Q

bulky filler proteins

A

resist compression, proteoglycans and GAGs in cartilage

76
Q

cross-linking proteins

A

fibronectin and laminin

77
Q

basal lamina

A

specialized ECM, links tissues with connective tissues

78
Q

what is different in cancer cells?

A
  • do no senesce (active telomerase or inactive p53)
  • lack growth factor dependence
  • lack anchorage dependence (grow in suspension)
  • no cell-cell contact inhibition (cells pile up on each other)
79
Q

proto-onocogenes

A

stimulate growth code for important proteins at all levels of cell growth pathway

80
Q

myosin I

A

monomeric, stand alone vesicle motor; walk along actin filament towards + end

81
Q

myosin II

A

dimerizes, associates with light chains; head contain ATPase motor domains; phosphorylation of light chains leads to smooth muscle contraction

82
Q

classes of signaling molecules

A
  • small, diffusable molecules
  • hydrophobic (steroids and eicosinoids)
  • hydrophilic (peptides, amino acid de
  • sensory signals
83
Q

what affects membrane fluidity

A
  • temperature
  • length and degree of unsaturation: longer chain has more van der waals attractions
  • cholesterol content: planar and stiff (decreases fluidity by preventing rotation, can increase by preventing packing)
  • lipid rafts are less fluid
84
Q

Shrimpton Diseases & MOI

A 
Hemophilia A; XLR
CF; AR
α-1-Antitrypsin def; AR
DMD; XLR
Tay Sachs; AR
Sickle cell disease; AR
α and β Thalassemia; AR

Dynamic Mutations
Fragile X X!?
HD AD
DM AD

85
Q

flippase

A

catalyzes transfer of specific phospholipids to cytosolic monolayer; gives asymmetric distribution of phospholipids

86
Q

scramblase

A

catalyzes transfer of random phospholipids from one monolayer to another

87
Q

replication stress response

A

replication forks are vulnerable to DNA damage or nucleotide shortage; checkpoint mechanisms halt replication if this happens and up regulates repair proteins

88
Q

DNA repair mechanisms

A
  • template-independent damage (direct reversal)
  • ssDNA damage (requires intact copy)
  • dsDNA breaks: NHEJ is preferred in humans, homologous recomb is better though
89
Q

ribosome biogenesis

A

45 rRNA is transcribed, acts as a precursor that is then processed by enzymes to make 28S, 18S, and 5.8S; 5S; 18S leaves to make 40S and 5S joins to make 60S; large and small subunits are assembled and then exported out of nucleus to come together as 40S and 60S

90
Q

conjugation

A

horizontal gene transfer through plasmids

91
Q

transformation

A

pick up DNA from environment

92
Q

transduction

A

bacteriophages pick up flanked DNA which can then be delivered to new host

93
Q

transposons

A

code for transposases that catalyzes transposition; retrotransposons move via RNA intermediate

94
Q

retroviruses

A

ssRNA genome that gets converted to dsDNA by viral reverse transcriptase; viral promoters can be very active so insertion can inappropriately turn on neighboring genes

95
Q

why are flanking intragenic markers more useful than markers on the same side?

A

it would take a double crossover rather than a single crossover to cause an error with flanked markers

96
Q

adaptin

A

mediate the formation of vesicles by clathrin-coated pits through interaction with membrane-bound receptors

97
Q

what are the genetic/biochem differences between type A, B, and ABO?

A

differ in the transferase enzymes encoded at ABO locus, adds terminal sugars on the glycoproteins and glycolipids on the surface of the blood cell

  • type A: GalNAc
  • type B: Gal
  • type AB: both
  • type O: no terminal sugar

GER Unit 1 (2 decks)

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