Molecular Biology and Genetics Lecture Notes

A comprehensive set of vocabulary flashcards covering basic and advanced topics in molecular biology, genetics, and cell physiology as presented in the lecture notes.

Stem cells

Cells found in all multicellular organisms that can divide and differentiate into diverse specialized cell types and renew themselves to produce more stem cells.

Self-renewal

The ability of stem cells to go through numerous cycles of cell division while maintaining an undifferentiated state.

Potency

The capacity of a stem cell to differentiate into specialized cell types.

Totipotent

Stem cells that can differentiate into embryonic and extraembryonic cells, capable of making a complete organism.

Pluripotent

Stem cells that can differentiate into any of the three germ layers and gonadic cells, but not extraembryonic cells.

Multipotent

Progenitor cells that can differentiate into many kinds of somatic cells, but not gonadic cells.

Unipotent

Cells that can differentiate into only one type of cell but can still renew themselves.

Induced Pluripotent Stem Cells (iPSC)

Differentiated cells that have been reverted back into stem cells using transcription factor treatment, a discovery made by S. Yamanaka and J. Gurdon.

Haematopoietic stem cell transplantation (HSCT)

Commonly known as bone marrow transplantation; the only currently used stem cell treatment, primarily for diseases like multiple myeloma and leukemia.

In vitro experiment

An experiment performed "in a glass," usually in a cell-free environment; generally cheap and fast but offering limited conclusions.

In vivo experiment

An experiment performed "within the living," using whole, living organisms.

Ex vivo experiment

Experiments where cells are alive but have been removed from the organism to model organ functions.

In silico experiment

Experiments performed within computers, such as active substance screening or enzyme-ligand docking.

In situ studies

Studies where the original localization of the sample is preserved, such as histology.

Primary Cell Culture

Cells isolated directly from tissues which have a limited lifespan known as the Hayflick limit.

Immortalized Cell Line

Cells, often cancer cells like HeLa or Jurkat, that undergo infinite divisions due to active telomerase or mutations evading senescence.

Knock-out (KO)

An organism where one specific gene has been erased or damaged.

Transgenic organism

An organism where a gene from another species has been inserted.

Peptide bond

A bond formed when the amino group ($-NH_2$) of one amino acid reacts with the carboxyl group ($-COOH$) of another, releasing a water molecule.

Aldose

A monosaccharide where the oxo-group is located at the end of the carbon chain, such as glucose.

Ketose

A monosaccharide where the oxo-group is attached to an intermediate carbon atom, such as fructose.

Endosymbiotic Theory

The theory suggesting that mitochondria and chloroplasts originated from once free-living prokaryotes.

Atomic Number (Z)

The unique number of protons in the nucleus characteristic of an element.

Mass Number (A)

The total number of nucleons (protons plus neutrons) in the nucleus.

Isotopes

Clusters of atoms that have the same number of protons but different numbers of neutrons.

Electronegativity (EN)

A unitless number characterizing the electron-attracting ability of atoms in a bond.

Hydrogen bond

The strongest secondary bond, formed when a hydrogen atom is attracted to a non-bonding electron pair of a highly electronegative atom.

Van der Waals interactions

Weak bonds (about $1/20^{th}$ the energy of a primary bond) resulting from charge asymmetry within molecules.

Osmosis

A special form of diffusion where a solvent (water) passes through a semipermeable membrane.

Genome

The total DNA content of a cell.

Gene

A region of DNA that controls a discrete, hereditary characteristic and usually specifies a functional product like RNA or protein.

Exons

Actual gene sequences that encode proteins, making up about $1.5\%$ of the human genome.

Introns

Non-coding segments of DNA located within genes that are removed during RNA processing.

Transposons

DNA sequences that move across the genome, making up roughly $45\%$ of the human genome.

Fluid Mosaic Model

A model of the cell membrane describing it as a fluid structure composed of various parts like lipids, proteins, and carbohydrates.

Nuclear Pore Complex (NPC)

A ring-like structure made of nucleoporin proteins that regulates selective transfer between the nucleus and cytoplasm.

Euchromatin

The active, functional part of DNA that is loosely folded and being transcribed into genes.

Heterochromatin

The inactive, solid-state phase of DNA that is not currently being transcribed.

Autophagy

A process where an organelle is surrounded by a double membrane to form an autophagosome, which then fuses with a lysosome for digestion.

Nucleosome

The lowest level of chromosome organization, consisting of DNA wound around a histone octamer (two copies each of H2A, H2B, H3, and H4).

Pseudogenes

Defective copies of genes that contain stop codons or frameshifts and have lost their function due to mutation.

FISH (Fluorescent In Situ Hybridization)

A technique using small, fluorescently labeled oligonucleotides to detect specific nucleic acid sequences.

DNA supercoiling

A process where DNA is more compact than its relaxed counterpart; negative supercoiling is critical for fitting chromosomes into the nucleus.

Okazaki fragments

Short, discontinuous DNA segments synthesized on the lagging strand during DNA replication.

Semiconservative replication

The mode of DNA replication where each new DNA molecule contains one template strand from the parental DNA and one newly synthesized strand.

ddNTP (Dideoxynucleotide)

A nucleotide lacking a 3' $-OH$ group, used in Sanger sequencing to act as a chain terminator.

Taq polymerase

A heat-stable DNA polymerase isolated from Thermus aquaticus, essential for withstanding the denaturation steps in PCR.

Melting temperature ($T_m$)

The temperature at which $50\%$ of DNA strands bind to primers, calculated as $T_m = 4(G+C) + 2(A+T)$.

Polycistronic mRNA

A single mRNA molecule found in prokaryotes that contains the code for multiple different proteins.

Sigma factor

A prokaryotic protein essential for promoter recognition that directs RNA polymerase to specific sets of genes.

RNA editing

An enzymatic process involving the deamination of specific nucleotides (e.g., C to U) to produce different proteins from the same gene.

CRISPR-Cas system

A bacterial adaptive immune response used as a gene-editing tool, where crRNA guides Cas proteins to degrade matching DNA sequences.

Genetic Code Degeneracy

A property of the genetic code where most amino acids are encoded by more than one codon.

Wobble hypothesis

The suggestion that the third base of a codon is variable, allowing a single tRNA to recognize multiple codons.

Svedberg unit (S)

A sedimentation coefficient measuring the rate at which components sediment in a centrifuge based on molecular weight and shape.

Ubiquitin-dependent pathway

A highly selective process for protein degradation where targets are marked with ubiquitin and destroyed by the 26S proteasome.

Restriction Point (R point)

An irreversible transition point in the G1 phase where a cell commits to the cell cycle based on nutrients and external signals.

Cyclin-dependent kinases (Cdks)

A family of serine/threonine protein kinases that require cyclins to become active and regulate the cell cycle.

Bacteriostatic antibiotics

Agents that inhibit the growth and reproduction of bacteria without directly killing them.

Bactericidal antibiotics

Agents that actively kill bacteria.

MIC (Minimal Inhibitory Concentration)

The lowest concentration of an antibiotic that inhibits visible bacterial growth.

Kinesins

Motor proteins that move toward the plus end of microtubules.

Cytoplasmic dynein

A motor protein that moves toward the minus end of microtubules.