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Bio Final Exam
| Term | Definition |
|---|---|
| Gene | region of DNA encoding a single polypeptide OR encoding an RNA with a function (rRNA, tRNA, small noncoding RNAs) |
| Transcription | polymerization of NTPs in 5’ -> 3’ direction catalyzed by RNA pol. Process that builds mRNA using DNA within a gene. |
| Template strand | DNA strand that is copied by RNA polymerase |
| Polarity | a difference in electronegativity (we consider C, N, and H to be the same) |
| Hydrogens bonds | are formed between two hydrogens that are attached to O, N, or F. |
| Nonpolar substances are | hydrophobic |
| Van der Waals interactions | minute partial charge on one molecule induces an opposite partial charge in the nearby molecule and causes an attraction, caused by random motion of electrons |
| Primary structure of proteins | unique sequence of amino acids |
| Secondary structure of proteins | interactions between functional groups in backbone |
| Tertiary Structure of proteins | interactions between R groups (often far apart in sequence) ○ Hydrogen bonding, hydrophobic interactions/van der Waals, disulfide bridges, ionic bonding |
| Quaternary structure of proteins | combination of multiple polypeptide subunits |
| Molecular chaperones | can facilitate protein folding |
| Enzymes | are proteins that act as catalysts |
| Enthalpy | total energy of a molecule (potential + kinetic) - determines exothermic and endothermic |
| Gibbs free energy | the amount of energy in the reaction available to do work |
| Michaelis-Menten kinetics | Vmax and Km |
| Enzymes are affected by | temperature, interactions with other molecules, and modifications of its primary structure |
| Competitive inhibitor | a process where an inhibitor competes with a substrate for binding to the active site of an enzyme, preventing the substrate from binding and thus inhibiting the enzyme's activity. |
| Noncompetitive (allosteric) inhibitor | a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds to a site other than the active site, resulting in a conformation change of the enzyme. |
| Catabolic | breaks down larger molecules into smaller units, releasing energy, |
| Anabolic | build complex molecules from simpler ones, requiring energy |
| Lipid | carbon-containing and insoluble in water |
| Fatty acid | a simple lipid consisting of a hydrocarbon chain bonded to a polar carboxyl functional group |
| Only single bonds | saturated |
| With double bonds | unsaturated |
| Steroids | bulky, four-ring structure - hormone, cholesterol |
| Fats | three fatty acids that are linked to a three-carbon molecule called glycerol ○ Primary role: energy storage ○ Joined by ‘ester linkage’ |
| Phospholipids | glycerol that is linked to a phosphate group and two hydrocarbon chains of fatty acids ○ Form plasma membranes; are amphipathic |
| In water, phospholipids form | a micelle or a bilayer |
| Liposome | artificial vesicle formed by mixing amphipathic lipids, such as phospholipids, together in an aqueous solution |
| Membrane is selectively permeable | small nonpolar molecules cross quickly |
| adding cholesterol molecules to membranes | reduces their permeability |
| Phospholipids are in constant lateral motion, lower temperatures | less fluid and less permeable |
| Diffusion | spontaneous movement |
| Passive transport | does not require energy and moves molecules down/ along the concentration gradient/electrical gradient |
| Fluid-mosaic model | Proteins can be amphipathic as well ○ Can be integral/transmembrane or peripheral |
| Active transport | requires energy to move molecules against their concentration gradient. |
| Channel proteins | facilitate diffusion - usually for ions or small polar molecules, electrochemical gradient |
| Gate channels | open or close in response to a signal |
| Carrier proteins | selectively pick up a solute on one side of the membrane, then drop it off on the other side |
| Pumps | perform active transport using ATP - ALWAYS use energy, even if with gradient ○ Ex. Sodium-potassium pump |
| Secondary active transport/cotransport | – an ATP pump provides the energy in the form of a gradient that is used to power the movement of a different solute in a directed manner, often against its particular gradient |
| Advantages of compartmentalization | separate chemical reactions, more efficient chemical reactions |
| Organelle List | nucleus, ribosomes, smooth/rough ER, golgi apparatus, lysosomes, vacuoles, peroxisomes, mitochondria, chloroplasts, cytoskeleton, plasma membrane, cell wall/extracellular matrix |
| Nuclear Transport process | Nuclear envelope (two membranes) is around nucleus - has a nuclear pore complex ○ Several types of RNA leave the nucleus (rRNA, mRNA) ○ Proteins are only allowed into the nucleus if they have an NLS |
| The Endomembrane System Manufactures, Ships, and Recycles Cargo process | in peroxisomes, mitochondria, and chloroplasts are also actively imported. signal sequence binds to a signal recognition particle, tells protein synthesis to stop. The complex moves to the rough ER membrane. Transported to Golgi through vesicles |
| Lysosome | are membrane-bound organelles found in nearly all animal cells, responsible for breaking down macromolecules, old cell parts, and microorganisms using digestive enzymes. |
| Phagocytosis | the process by which a cell engulfs and digests large particles, such as pathogens or debris, using its plasma membrane to form a compartment called a phagosome. |
| Endocytosis | a cellular process where substances are brought into the cell by engulfing them in a vesicle formed from the cell membrane. |
| Exocytosis | the process by which a cell releases substances, such as proteins, by enclosing them in vesicles that fuse with the cell membrane, allowing the contents to be expelled outside the cell. |
| Actin filaments | globular actin polymerizes into filamentous actin with help from ATP ○ Function: cell shape, cell movement, divide animal cells in two, move organelles/cytoplasm ■ Works with myosin – cytokinesis, cytoplasmic streaming, cell crawling |
| Intermediate filaments | Keratins, laminins, etc. wound into thick fibers, no polarity ○ Function: cell shape, nuclear laminins |
| Microtubules | alpha and beta dimers ○ Originate from MTOC, usually centrosome ○ Function: cell shape (push), move cells with flagella/cilia, move chromosomes, cell plate, provide tracks form intracellular transport |
| Kinesins | are motor proteins that move along microtubules in cells, typically transport cargo toward the plus end |
| Dyneins | are motor proteins that move along microtubules in cells, move toward the minus end |
| Metabolism | sum of all chemical reactions occurring within a cell |
| Metabolic pathways | series of individual reactions where the product of one reaction becomes the substrate for the next reaction |
| Anabolism | synthesis of most complex organic compounds - products are combinations or polymers of substrates - uses ATP or other forms of energy Example: Protein synthesis |
| Catabolism | the degradation of organic compounds - products are subunits of reactants - Includes the breakdown of carbohydrates, lipids, and proteins to release free energy - Energy is released in small, controlled reactions |
| Reductant | electron donor = reducing agent Ex. NADH |
| Oxidant | electron acceptor = oxidizing agent Ex. Oxygen Ex. NAD+ |
| Monosaccharides | monomer subunits = simple sugars |
| Polysaccharides | many monosaccharides linked together Synthesized by condensation reactions |
| Kinases | catalyze phosphorylation of substrates ATP as source of phosphate |
| Glycolysis | first step in aerobic cellular respiration, breakdown of glucose as a first, energy-releasing step in cellular respiration, occurs in cytosol , does not require oxygen |
| Glycolysis produces | 2 pyruvate (3C each) + 2ATP + 2NADH |
| Isomerases/mutases | catalyze change in molecular organization without altering atoms present No atoms gained or lost from molecule, just rearranged |
| Dehydrogenase | catalyze reactions that transfer e- and H+ from substrate - e- accepted by oxidizing agent |
| Second step of aerobic cellular respiration | pyruvate processing where conversion of pyruvate into acetyl CoA takes place, occurs in mitochondrial matrix, produces some NADH, CO2 released as waste |
| Mitochondria | site of aerobic respiration |
| Mitochondrial structure | two lipid bilayers surrounding an inner “matrix” Outer mitochondrial membrane (OMM) Inner mitochondrial membrane IMM |
| cristae | infoldings of IMM |
| Mitochondrial matrix | protein-rich region surrounded by IMM |
| Intermembrane space | space between IMM and OMM |
| ATP synthase | protein in the IMM used to pump H+ ions |
| Third step of aerobic cellular respiration | Krebs (TCA/citric acid) cycle |
| Krebs (TCA/citric acid) cycle | acetyl-CoA oxidized to CO2, occurs in mitochondrial matrix, produces some NADH, FADH2, and ATP, CO2 released as waste |
| Third step of aerobic cellular respiration | Oxidative phosphorylation |
| Oxidative phosphorylation | using the electron chain transport to use oxygen to phosphorylate ADP to ATP, occurs across inner mitochondrial membrane |
| fermentation | takes place to generate lactic acid (or alcohol) in organisms that are undergoing glycolysis in the absence of oxygen |
| aerobic respiration | uses oxygen as a final electron acceptor (oxidizing agent) in a process that regenerates NAD+. |
| Nucleic acids | RNA and DNA |
| Nucleotides have | a phosphate group, 5-carbon sugar, and nitrogenous bases |
| Ribose has | two OH groups and is for RNA |
| Deoxyribose has | one OH group and is for DNA |
| Nitrogenous Bases | Cytosine, Guanine, Adenine, Thymine, and Uracil (RNA) |
| Phosphodiester linkage | is a chemical bond that forms between the phosphate group of one nucleotide and the sugar molecule of another nucleotide, creating the backbone of DNA and RNA. |
| DNA replication | making a copy of genomic DNA |
| Basic mechanism of DNA replication | 1) Complementary strands separate 2) New nucleotides added that are complementary to both strands • Results in 2 identical copies |
| Semiconservative replication | new molecule has ½ old DNA and ½ new DNA |
| Replication mechanism | 1) Initiation – starting replication 2) Elongation – lengthening DNA strands 3) Termination – completion of DNA synthesis |
| Origin of replication | specific DNA sequence where replication begins • Recognized by specific proteins, which separate DNA strands to form bubble • Lots of origins in eukaryotic genomes |
| Replication fork | “Y-shaped” DNA region at end of bubble |
| Helicase | enzyme that unwinds or separates DNA strands |
| Single-stranded DNA binding proteins (SSBs) | stabilize and protect singles-tranded DNA |
| DNA polymerase | enzyme that catalyzes the linking together of nucleotides |
| Primase | enzyme that catalyzes synthesis of a ‘primer’ of RNA nucleotides on which DNA polymerase can begin replication |
| DNA polymerase III | lengthens new DNA strands in 5’ to 3’ direction • Adds incoming dNTPs complementary to template strand |
| Leading strand | new DNA strands synthesized continuously – moving in same direction as helicase |
| Lagging strand | new strands synthesized discontinuously – moving in opposite direction as helicase |
| Okazaki fragments | short DNA sequences formed on lagging strand • Problem: ‘primers’ are made of RNA, not DNA • RNA primers replaced by specialized polymerase (DNA polymerase I) |
| Ligase | enzyme that links Okazaki fragments • Catalyzes phosphodiester bond formation |
| End result of replication | Two identical daughter DNA molecules |
| Phenotype | outward appearance of a trait |
| heterozygote | If an individual has two different alleles, one allele is dominant to the other in determining phenotype |
| Chromosome | organized structure of DNA and protein that carries our genetic information |
| Sex chromosome | chromosome that determines the sex of an individual |
| Autosomal chromosome | chromosome that does not determine the sex of an individual |
| Locus | specific location of a gene (DNA sequence) on the chromosome |
| Allele | one of a number of alternative forms of the same gene |
| Dominance | a dominant allele will have its phenotype expressed if present; a recessive allele will exhibit its phenotype only in homozygotes for that allele |
| Recessive mutation | mutated allele has lost its function and recessive to wild-type |
| Dominant mutation | mutated allele has gained function (or lost regulation) is often dominant to the wild-type allele |
| Co-dominance | cross between two organisms with different phenotypes results in offspring of a third phenotype in which both parental traits appear together – proteins from both alleles are functional and produced |
| Independent assortment of alleles | The inheritance pattern of one gene does not impact the inheritance pattern of another gene (if they are on separate chromosomes) |
| Incomplete dominance | Seeing a partial phenotype in heterozygotes due to haploinsufficiency and a stronger one in homozygous recessive. |
| Dominant allele | A variant of a gene where you will see the phenotype in both heterozygotes and homozygotes containing that allele. |
| Recessive allele | A variant of a gene where you will see the phenotype only in homozygotes with only this allele. |
| Lethal allele | Typically caused by a loss-of-function allele, Because the gene is essential for some key function(s), organisms that are homozygous for the loss-of-function allele do not develop/survive. crosses are produced in a 2:1 mutant:wild-type ratio |
| Template strand | DNA strand that is copied by RNA polymerase |
| Coding strand | Not copied and RNA molecules have the same sequences as it |
| Transcription start site (TSS) | where RNA polymerase actually begins transcription |
| Promoter (Upstream): | DNA sequence that determines if and where RNA pol will start transcription |
| Transcription factors | proteins that bind to DNA to regulate transcription and recruit RNA polymerase |
| Why would a cell bother to transcribe DNA into RNA? | Amplification, regulation, evolution (RNA likely came first), and protection of DNA in the nucleus |
| RNA pol I: | Transcribes rRNA and some small RNAs |
| RNA pol II: | Transcribes mRNA and some small RNAs |
| RNA pol III: | Transcribes tRNA and some small RNAs |
| Basal txn factors for RNA pol II | TATA-binding proteins bind to the sequence and then TBP-associated factors bind to the TBPs |
| To begin transcription | kinase bound to txn factor activity phosphorylates specific amino acids in C-terminal domain (CTD) |
| RNA pol II comes off | Conserved DNA sequence) that recruits proteins that modify the 3’ end of the new mRNA |
| mRNA processing | 5’ capping, 3’ polyadenylation, splicing (pre-mRNA to mature mRNA) |
| 5’ cap: | Guanine gets attached to 5’ end of pre-mRNA -> 5’ carbon of G gets linked to 5’ carbon of 1st nucleotide in mRNA → - Methyl groups are attached to nucleotides |
| 5' cap and 3’ polyadenylation helps with: | Protects mRNa from degradation by enzymes, Recognized by other proteins for transport out of nucleus, Recognized by proteins that help the mRNA associate with ribosomes |
| 3’ polyadenylation | ~30 – 250+ ‘A’ nucleotides are attached to 3’ end of RNA – added by a complex of proteins that recognize “AAUAAA’ sequence, cut the mRNA, and recruit PolyA-polymerase |
| RNA splicing | put together exons, remove introns |
| Process of RNA splicing: | snRNPs recognize specific sequences in pre-mRNA at splice sites, forming a spliceosome complex with the mRNA |
| Central Dogma | DNA-DNA (replication) DNA-RNA (Transcription) RNA- Protein (Translation) |
| mRNA | acts as a messenger carrying DNA encoded info and is translated into a protein. |
| rRNA | forms part of the structure of ribosomes |
| tRNA | carries amino acids to the ribosome during translation and contains anti- codons (3 nucleotides complementary to the mRNA codons) |
| One snRNP creates 5’ splice site | attaches 5’ end of intron to an ‘A’ nucleotide near 3’ end of intron, forming a lariat structure Then creates 3’ splice site, and lariat structure is released- – phosphodiester bond between exons |
| How does mRNA encode for proteins? | codons that are non-overlapping and have a wobble! |
| ORF | Open reading frame. Starts at AUG and ends at first in frame stop codon (UAA, UAG, or UGA) |
| Point mutation | Missense mutation: nucleotide change causes change in a.a sequence. ex. UAC (Tyr) - UGC (Lys) |
| Silent Mutation | nucleotide change does not create change in a.a sequence. ex. UAC (Tyr)- UAU (Tyr) |
| Nonsense Mutation | nucleotide change causes an early stop codon. ex. UAC (Tyr)- UAG (stop) |
| Frameshift Mutation | addition or deletion of nucleotide that causes shift in reading frame. ex. UAC UAC UAC (Tyr-Tyr_Tyr) to UAC GUAC UAC (Tyr- Val-Leu) |
| The machinery of translation | ribosome (small and large subunit) and tRNAs |
| Ribosome has EPA sites reads from | reads from 3’ to 5’ |
| Epigenetics | non-nucleotide based information in the genome that exerts regulatory control over gene expression. |
| Nucleosome | DNA wrapped around histones |
| Acetylation | makes histones more open/ opens up the chromatin |
| Methylation | turns off genes, especially when promoter is methylated (looks packed) |
| HAT | does acetylation |
| HDAC | condenses it again |
| Why do cells regulate gene expression? | 1. cells differentiate. 2. conserve energy. 3. adapt |
| DNA sequences regulating transcription: | promoter-proximal elements, enhancer, silencer - activators or repressors bind |
| Promoter-proximal elements (PPE) | near promoter, not required, can increase or decrease txn, proteins: activators or repressors |
| reporter sequences | a way to study gene regulation sequences that are important for transcription |
| Enhancers | far away (both up and down stream), not required, increases txn, proteins activators |
| Silencers | far away, not required for txn, decreases txn, proteins: repressors |
| Reporter assays | promoter or regulatory sequence is placed near a reporter gene and the amount of txn is measured. |
| RISC (RNA induced silencing complex) | Small RNA binds mRNA target, Protein cuts mRNA target |
| Post-translational Modifications (PTMS) | Covalent modifications to amino acid. Phosphorylation and Ubiquitination |
| Phosphorylation | adds neg. phosphate to ser, thr, tyr often activates a protein |
| Ubiquitination | covalent attachment of ubiquitin to a protein , cuts up a protein |
| Heterochromatin | Tight packed and low transcription activity |
| Euchromatin | Loosely packed and high transcription activity |
| Histone acetylation | loosens the chromatin structure, making the DNA accessible to RNA polymerase |
| TATA box | sequence of repeated AT located in the promoter that recruits the TIC (transcription initiation complex). |
| RNAi | RNA interference process of small noncoding RNAs blocking translation of target mRNA molecules. |
| Small noncoding RNA | short strands of RNA that have a complementary sequence to their mRNA target. |
| Cell Signaling | the ability for all cells to produce, receive, and respond to external signals/conditions. |
| Ligand | a small signaling molecule that binds and forms a complex with a biomolecule/receptor. |
| Receptor | biomolecule (protein) that changes shape (or conformation) upon ligand binding. |
| 1st step of Cell Signaling | Receptor recognition/binding of signal signal |
| 2nd step of cell signaling | Signal transduction/ intracellular signaling |
| 3rd step of cell signaling | cell response/ target proteins |
| 4th step of cell signaling | turn off the signal |
| G-protein coupled receptor (GPCR) | Transmembrane receptor, 7-pass, works with G-proteins |
| G-proteins act as | a molecular switch that use GTP/GDP to turn on/off signaling |
| Bound GTP | on or activated |
| Bound to GDP | on or activated |
| GTP hydrolysis activity | cleave GTP to GDP |
| GTPase Activating protein (GAP) | Promotes GTP hydrolysis |
| Guanine Exchange Factor (GEF) | Promotes release of GDP so GTP can bind |
| Extracellular matrix (ECM) | network of secreted proteins and carbohydrates outside of the lipid bilayer. |
| Collagen | Three polypeptide chains -strong |
| Fibronectin | Large glycoprotein -domains to interact w/ other proteins |
| Laminin | Large glycoprotein- interacts w/ other laminins or ECM molecules |
| ECM Functions | support/structure for cell, cell-cell interactions/ communication, provides protection |
| Transmembrane proteins | connecting inside cell w/ extracellular environment |
| Integrin | cytoskeletal and extracellular interaction |
| Cadherin | cell adhesion proteins binds to cadherins on adjacent cells |
| Epithelia (skin cells) | Cell-cell interactions: tight junctions stitching adjacent cells together. |
| desmosomes | spot welds |
| Gap Junctions | Pores that allow ions and molecules to flow btw cells. |
| Interphase | DNA "loosely" packed. includes G1, S, G2 phases |
| G1 | each chromosome contains a single, double-stranded DNA molecule. Cell contains a single centrosome organizing the microtubule network |
| Centrosome | (microtubule organizing center (MTOC)) group of proteins that organize microtubules |
| Microtubule minus ends are toward | centrosome plus ends away |
| S phase | DNA replicates (forming two sister chromatids= identical DNA molecules), centrosome also duplicates |
| G2 | Each chromosome now contains two identical copies of each chromosome and two centrosomes |
| Mitosis | condensed chromosomal DNA gets equally distributed into daughter cells. Microtubules and associated proteins drive the movement of chromosomes (DNA) |
| After Mitosis | the daughter cells (in G1) have exactly the same DNA as the mother cell had (in G1) |
| Mitosis Prophase | Nuclear envelope begins to break down. Two centrosomes separate mitotic spindle made of microtubules forms btw them. Chromosomes begin condensation and become more tightly wound around histones. |
| Sister Chromatids | identical DNA molecules attached at centromere |
| Centromere | region of DNA bound by proteins that keep sister chromatids together |
| Kinetochore | complex of proteins associated with the centromere |
| cohesions | proteins that keep sister chromatids associated |
| Prometaphase | Nuclear envelope completes breakdown, centrosomes reach opposite poles and mitotic spindle between them. Kinetochore microtubules associate w/ kinetochores. Interpolar microtubules associate w/ microtubules from opposite direction of each cell. |
| Metaphase | chromosomes are moved to metaphase plate (midway between poles) |
| Metaphase checkpoint | pause in mitosis that waits for all chromosomes to attach to mitotic spindle and reach metaphase plate. |
| Anaphase | sister chromatids separate and move toward opposite poles. |
| How are sister chromatids allowed to separate from each other? | Loss of cohesion function |
| How do sister chromatids move towards opposite poles of the cell? | Pulled by disassembly of kinetochore microtubules |
| Telophase | Interpolar microtubules push opposite ends of cell apart. Sister chromatids reach opposite poles. DNA decondenses. Chromatin released from microtubules. Nuclear envelope reassembles. Now you have have two separate nuclei each w/ identical DNA content. |
| Cytokinesis | divison |
| Chromosome | 1 DNA molecule and associated proteins Or 2 DNA molecules (sister chromatids) after DNA replication |
| Diploid | two of each ch’some type (“Pair” of chromosomes of each type) = 2N. One ch’some of pair from mother, other ch’some from father |
| Haploid | one of each chromosome type = 1N |
| Homologous chromosomes | chromosomes of the same type |
| Somatic cells | “body” cells -> diploid (2N) |
| Gametes | “sex” cells -> haploid (N) |
| Germ cells | haploid gametes and the diploid cells they are derived from |
| Meiosis | process of generating haploid cells from diploid |
| Germ line | continuous line of cells passed on from generation to generation |
| Meiosis | producing 4 haploid cells from 1 diploid cell |
| Meiosis I (first cell division of meiosis) | separation of homologous chromosomes |
| Meiosis II (2nd cell division of meiosis) | separation of sister chromatids |
| Before Meiosis | G1->S-> G2 and DNA and centrosomes duplicated. |
| Meiosis Prophase I | - Nuclear envelope breakdown Separation of centrosome pairs and meiotic spindle formation Chromosome condensation Synapsis of homologous chromosomes Proteins link DNA together along entire length of homologous chromosomes |
| Synaptonemal complex | complex of proteins that links homologous ch’somes during synapsis |
| Tetrad | complex of two homologous chromosomes and their sister chromatids in synapsis |
| Homologous recombination (crossing over) | occurs between homologous chromosomes the two homologous chromosomes “break” at the exact same place and swap DNA at that point! Each sister chromatid has some maternal and some paternal DNA!! |
| Meiosis Prometaphase I | paired homologous ch’somes attached to kinetochore microtubules |
| Meiosis Metaphase I | paired homologous chromosomes move to metaphase plate - Crossing over has been completed, but tetrads remain together |
| Meiosis Anaphase I | homologous chromosomes separate toward poles |
| Meiosis Telophase I | chromosomes complete movement toward poles |
| Meiosis Cytokinesis | cytoplasm divided |
| Independent assortment | each chromosome pair sends chromosome from male or female randomly toward opposite poles - end up with mixture of maternal and paternal chromosomes in each daughter cell produced Sister chromatids remain attached to each other |
| At end of Meiosis I: | have two daughter cells Each has one homologous chromosome from each original pair - Each contains a mixture of maternal and paternal DNA -> due to homologous recombination and independent assortment |
| Meiosis II does not have | No DNA duplication |
| Meiosis II Prophase II | meiotic spindle forms and attaches to kinetochores |
| Meiosis II Metaphase II | chromosomes move to metaphase plate |
| Meiosis II Anaphase II | sister chromatids move to opposite poles |
| Meiosis II Telophase II | nuclei reform |
| Meiosis II Cytokinesis | Cytoplasm separate |
| End of Meiosis II: | Four haploid daughter cells DNA content is different in each |
| Spermatogenesis | meiosis and differentiation (cell specialization) to produce sperm cytoplasm divided equally => 4 sperm per meiosis |
| Oogenesis | meiosis and differentiation to produce egg cytoplasm divided asymmetrically -> one egg (oocyte) + three polar body cells |
| Genetic variation | primary reason for the evolution of sexual reproduction |
| Sources of genetic variation: | 1. Homologous recombination (crossing over) 2. Independent assortment (during meiosis) 3. Random fertilization – any sperm could meet any egg! |
| Non-disjunction | failure of homologous chromosomes or sister chromatids to segregate properly - End up with incorrect number of chromosomes in gametes! |
| How can protein activity changes alter what is happening in each “phase” of the cell cycle? | proteins involved were identified by research groups working on model organisms (yeast, amphibians, sea stars) = non-human organisms with characteristics that make them easier to study |
| Cyclin proteins | Proteins “cycled” in abundance during cell cycle |
| G1/S cyclins | most abundant at end of G1 and when cell enters S-phase |
| G2/M cyclins | most abundant at end of G2 and when cell enters mitosis |
| Are cyclins involved in the cell cycle? What do they do? | 1. Cyclin proteins bind to another protein that is important for cell cycle control 2. The binding of cyclin to this 2nd protein activates enzymatic activity in the 2nd protein 3. This other protein can switch additional, specific proteins “on” or “off" |
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