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MolekylærMedisin > Introduction > Flashcards

Introduction Flashcards

1
Q

Nucleolus

A

transcription of rRNA and preassembly of ribosomes
inside the nucleus

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2
Q

Cell cycle

A

G1: protein synthesis, organelle production, cell growth, longest and variable

G0: G1-arresten cells, terminally differentiated cells (muscle cells, neurons)

S: replication of chromosomes

G2: cell prepares for mitosis

M: mitosis

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3
Q

Mitosis

A

Prophase: condensation of chromosomes, spindle formation

prometaphase: nuclear envelope breaks apart

Metaphase: chromosomes line up between the spindle poles

Anaphase: separation of sister chromatids, movement to opposite poles

telophase/cytokinesis: formation of nuclear envelope, decondensation of chromosomes, cell division (cytokinesis)

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4
Q

Regulation of the cell cycle

A

a strict control of cell cycle is essential for the organism

regulated by cell cycle-specific cyclins and cyclin-dependent kinases (CDKs)

CDKs are activated by cyclins (complex) and inhibited by CDK inhibitors

CDK phosphorylates (activates) nuclear target proteins that drives the cell cycle

different cyclins are expressed/degraded in different phases of the cell cycle

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5
Q

Cell cycle arrest

A

CDK inhibitors (CKIs) arrest the cell cycle under conditions like:
- contact with other cells
- DNA damage
- Terminal cell differentiation
- senescence

CKIs are often down-regulated in cancer!!

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6
Q

Apoptosis

A
  • normal physiological mechanism in multicellular organisms
  • important for development (separation of fingers and toes in vertebrates=
  • ca 0,1% of the cells in your body die every day by apoptosis (cell homeostasis)
  • protects against cancer and other dieases (elimination of mutated or virus-infected cells)
  • Abnormal apoptosis may result in neurodegenerative diseases (Alzheimer, Huntington, Parkinson) and tissue damage after stroke/heart attack
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7
Q

Apoptosis mechanisms - two main pathways

A

Extrinsic pathway: external signal, ligand binding (Fas ligand to Fas receptor), which activates caspase-8, which triggers effector caspases (the executioner) to cleave their substrate protein and drive the cell into apoptosis

Intrinsic pathwaY: internal signal activates mitochondria to release cytochrome C. Cytochrome C and Apaf-1 (apoptotic protease activating factor) bind together, and with the help of ATP generates the apoptosome, which activates caspase 9, which in turn activates the effector caspases (like caspase 3)

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8
Q

Caspases

A

Initiators: 2, 8, 9, 10

executioners: 3, 6, 7

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9
Q

Activation of procaspases

A

Inactive procaspase is activated by dimerization and auto-proteolytic cleavage

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10
Q

DNA replication

A

cellular DNA must be copied before a cell can divide

each strand serves as a template for a complementary strant (AT + GC). Semiconservative (old strand + new strand = new double helix)

DNA is synthesized in 5’ -> 3’ direction

replication is discontinous on the lagging strand (Okazaki)

Replication is initiated by the DNA polymerase alpha-complex, that generates a 7-10nt RNA primer (primase) extended by POLalpha

POL epsilon synthesizes the leading strand, POL delta the lagging

The helicase separates the strands, replication protein A (RPA) binds ssDNA and prevents reannealing

Supercoiling in front of the replication fork is twisted up by the topoisomerase, which releases topological stress

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11
Q

PCNA

A

Proliferating cell nuclear antigen

DNA clamp essential for DNA replication and coordination of the relication machinery

trimer that encircles the newly replicated DNA (dsDNA)

binds/coordinates the polymerases and other factors

important for processivity

master coordinator (hub) that can bind several hundred proteins involved in DNA replication, DNA repair, DNA damage tolerance (TLS), chromatin remodeling, cell signaling

proteins that binds pCNA contain PCNA-interacting motifs (PIP, APIM)

interaction is regulated by PTMs on PCNA and/or target proteins

Might be target for anti-cancer therapy??

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12
Q

CMG helicase - 11 subunit molecular machine

A

C = CDC45, M= MCM2-7 ring, G=GINS (heterotetramer)

MCM2-7 ring (heterohexamer) “ATPase motor, encircles ssDNA (template for leading strand) and travels 3’->5’ direction

CDC45 and GINS (heterotetramer) assessor factors are important for posiitoning

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13
Q

Topoisomerase - the topological stress releaser

A

Topoisomerase inhibitors are widely used in cancer treatment, often in combination with other cytostatic drugs

Irinotecan: colon cancer (+5 FU), small cell lung cancer (+cisplatin)

Etoposide: testicular cancer, lung cancer, lymphoma, leukemia, neuroblastoma, and ovarian cancer

Doxorubicin: breast cancer, bladder cancer, lymphoma, and acute lymphocytic leukemia

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14
Q

What happens at the chromosome ends (telomers)?

A

no obvious way to copy the most terminal sequences of the 3’ end, RNA-primer cannot be formed (boyond the end)

the chromosomes become slightly shorter for every round of replication/cell division

related to natural “ageing”

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15
Q

Embryonic stem cells, sperm cells, actiavted lymphoytes and many cancer cells express telomerase

A

telomerase is a cellular reverse transcriptase that extends the ends of linear chromosomes (telomeres). It contains an RNA component to which the ss 3’end of the chromosome hybridizes. Telomerase then adds several nucleotides

Most somatic cells do not express telomerase, and therefore tolerate ca 50-70 cell divisions

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16
Q

Telomerase mechanism

A

telomerase binds to 3’ flanking end of telomere that is complementay to the telomerase RNA

bases are added putside the strand using RNA as template (telomerase only binds part of its telomer-RNA to the DNA; the rest is left “open” for bases to be added on

telomerase relocates to the new end of the strand

second step is repeated

DNA polymerase complements the lagging strand

17
Q

Gene expression

A

A multistep process in which the genetic informaiton is used to produce a functional product - RNA or protein

Gene expression and its regulation are the fundament for cellular and organismal life - gene expression defines the cell type and function

Two main processes - trc and trn

18
Q

Transcription

A

The process where genes in the genome are copied into ssRNA molecules by RNA polymerase

19
Q

transcription

A

initiated at promoter regions - binding sites for general TFs

regulated by TFs (ca 10% of coding genes, DNA binding) and chromatin structure (epigenetic regulation)

Most RNA molecules are modified after transcription

Maturation of pre-mRNA to mRNA:
- 7mG-Cap
- polyA-tail
- removal of introns by splicing

20
Q

tRNAs

A

delivers AAs to the ribosome

transcribed (POLIII) as primary transcripts (1-5 tRNAs)

processed by RNase P (ribozyme) and endonucleases (RNqse D)

primary transcripts may contain introns adjacent to their anticodons that are removed

tRNA nucleotidyl-transferase adds CCA at the 3’ end

high content of covalent modifications (25% of the nucleotides)

21
Q

protein degradation

A

eliminates abnormal proteins

  1. lysosomal degradation (organelle, acidic pH, more than 50 hydrolytic enzymes (proteases), non-selective)
  2. targeted degradation of proteins marked with ubiquitin by the proteasome (ATP-dependent)

proteasome inhibitors: drugs that block the action of proteasomes. Approved for use in treating multiple myeloma

22
Q

methods in molecular medicine

A

separation (reduce complexity of a biological sample), electrophoresis (1D or 2D), chromatographic steps

isolation/purification (DNA; RNA; proteins): extraction, precipitation, chromatography

detection of specific DNAs, RNAs or proteins: Southern blot (DNA), Northern blot (RNA), Western blot (protein), MS

amplification:
- DNA/RNA - PCR and/or cloning
- proteins - cloning followed by heterologous expressionn (bacteria, yeast, insect cells)

sequencing (DNA/RNA)

genome engineering (CRISPR/Cas9)

cellular localization and trafficking (confocal mmicroscopy)

23
Q

NTNU covid test

A
  1. mucus sample from nose/throat
  2. sample is mixed with a chemical solution that causes the viral protein envelope to crack open
  3. magnetic nano-particles are added. virus RNA binds to the particles
  4. magnet pulls the RNA and nano-particles from the solution
  5. the RNA is released from the nanoparticles for analysis
  6. the RNA is analyzed in a PCR machine
24
Q

CRISPR/Cas9

A

clustered regulatory interspaced short palindromic repeats

RNA-guided nuclease (Cas9) that generates a ds break at the site that matches the RNA sequence

break is repaired by non-homologous end-joining (NHEJ), which is error prone

the “repair” results in indels, deletions, out of frame, premature stop codon, no active protein product

MolekylærMedisin (3 decks)

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