BSB Issues 150, Week 3
BSB Issues 150, Week 3 01:119:150
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This 8 page Class Notes was uploaded by Wendy Liu on Friday September 30, 2016. The Class Notes belongs to 01:119:150 at Rutgers University taught by Anthony Uzwiak in Fall 2016. Since its upload, it has received 104 views. For similar materials see Biology, Society, and Biomedical Issues in Biological Sciences at Rutgers University.
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Date Created: 09/30/16
Week 3: Intro to Stem Cell Research 29 September 2016 Biology, Society, and Biomedical Issues Professor Uzwiak Wendy Liu **go to bottom of page 7 to skip the (very condensed version of) basic cell biology** Cell Theory Cells are the functional and structural units of living organisms Activity of an organism is dependent on o individual cellular activity o collective cellular activity Heredity has a cellular basis Basic Animal Cell Plasma membrane – encloses cell o Fluid mosaic model – membranes are a mosaic of diff. proteins embedded in phospholipid bilayer; proteins can move around i.e. are “fluid” Hydrophilic portions of proteins/phospholipids exposed to water Hydrophobic portions are concealed in the non-aqueous environment within the membrane bilayer o Types of membrane proteins Integral – transmembrane proteins; span the hydrophobic interior Channels Carriers Peripheral – not embedded; attached to the surface Enzymatic activity Structure o Carbohydrates associated w/ exterior surface of membrane Cytoplasm – cellular material inside of cell; where most activity occurs o Cytosol – fluid that holds everything else o Mitochondria – turn potential energy in glucose into usable work energy (ATP) o Ribosomes – site of protein synthesis Ribosomal complex of RNA and protein Free in cytosol or bound to ER o Endomembrane system – membranes within the cell that interact directly through physical contact or indirectly through vesicles Vesicle – membrane-enclosed sacs that pinch off of one membrane, fuse with another Nuclear envelope Endoplasmic reticulum (ER) – network of membranous tubules and sacs (cisternae) Smooth ER – lacks ribosomes o Synthesize lipids, phospholipids, steroids o Carbohydrate metabolism o Drug detoxification o Calcium storage Rough ER – has ribosomes attached to surface o Ribosomes attached to ER synthesize secretory proteins Growing polypeptide enters receptor site of ER into cisternal space Polypeptide folds into native conformation o Enzymes add oligosaccharides to a secretory glycoprotein o Protein departs in vesicle pinched off of ER Golgi apparatus – modifies, packages, concentrates secretory proteins in vesicles from the ER Lysosomes – digests all major classes of macromolecules w/ hydrolytic enzymes Vacuoles – storage for nutrients/water Nucleus – contains genetic material o Most cells are mononucleate Large cells w/ lots of cytoplasm are multinucleate Red blood cells lack nuclei o Nuclear envelope – double membrane Outer membrane is continuous w/ ER Nuclear pores Selectively permeable o Chromatin Nucleosome = DNA wrapped around histone octamer core Chromatin condenses into chromosomes prior to cell division Cell Cycle Interphase – metabolic/growth/non-replication-related activities o G 1 growth phase w/ little cell division-related activities G – not part of division cycle; can last years 0 o S – synthetic phase: DNA replicates o G 2 very brief growth phase where enzymes and proteins necessary for division are synthesized Mitotic (M) phase – 2 daughter cells identical to mother cell o Mitosis – division of DNA Prophase – chromatin condenses into chromosomes Sister chromatids attached at centromere Nucleoli, nuclear membrane disappear Mitotic spindles (microtubules) attach to kinetochore protein of centromeres Spindles move chromatids to center of cell Metaphase – chromosomes align at middle of cell Metaphase plate – one set of chromosomes on each side of plate Anaphase – chromosomes split Centromeres split, each chromatid now a chromosome Spindles pull chromosomes toward poles Cell elongates, poles are pushed apart Shortest stage Telophase – chromosome mvmt. Stops Chromosomes uncoil into chromatin Nucleoli, nuclear membrane reform Spindles disassemble o Cytokinesis – division of cell body Peripheral microfilaments contract to squeeze the cells apart Split at cleavage furrow Meiosis – gamete production Meiosis I – reduction division o Prophase I – chromosomes form, nuclear envelope & nucleoli disappear Same as mitosis prophase Synapsis occurs: homologous chromosomes form tetrads & cross over at chiasmata (cross-over points) o Metaphase I – tetrads align on metaphase plate o Anaphase I – homologous (paternal & maternal) chromosomes separate Centromeres don’t break; sister chromatids still connected o Telophase I – same as mitosis telophase o Cytokinesis – split into 2 daughter cells Haploid in chromosomal number, but double in amount of DNA Meiosis II – like mitosis, but w/o DNA replication during interphase o 4 haploid daughter cells are genetically unique from mother cell Background on Heredity Autosomes – first 22 pairs of chromosomes: non-sex-based traits rd Sex chromosomes – last 23 pair: determines biological sex Karyotype – diploid chromosomal compliment of all cells Genome – genetic makeup of a cell o Diploid – 2 copies of DNA (one from maternal side, one from paternal side) o Haloid – 1 copy of DNA Chromosome – structure carrying genes o Only visible during cell division – the metaphase chromosome o Humans have 23 diploid, homologous pairs of chromosomes, 46 total Locus – location on chromosome Allele – matched genes at same locus on homologous chromosomes o Can code for same or alternate forms of a trait Homozygous – 2 alleles controlling a single trait are the same Heterozygous- 2 alleles controlling a single trait are different Dominant – one allele masks the expression of the other; written in capital letters Recessive – the masked allele; only expressed if both alleles are recessive; written in lowercase Genotype – individual’s genetic makeup; reflects allelic identity of that individual’s genes Phenotype – observable characteristics as a result of expression of the genotype Sources of genetic variation Independent assortment of chromosomes during metaphase I o Random alignment of tetrads: maternal and paternal chromosomes don’t all align on same side of the plate (possibility 2) o 2 different possible gametes resulting from independent assortment n = # of homologous pairs humans have 23 pairs = 8.5mil. possibilities Synapsis during prophase I – gene recombination o Same gene of paternal and maternal chromosomes can switch & cross over about a chiasma – results in recombinant chromosomes Random fertilization by sperm o Single egg fertilized by single sperm o Variation resulting from independent assortment and random fertilization: Possible eggs = 8.5mil. Possible sperm = 8.5mil. Possible zygotes = 8.5mil * 8.5mil. = 72 trillion Types of Inheritance Dominant-recessive i– dominant alleles mask recessive ones o Recessive traits – only expressed in homozygous recessive state o Punnet square – used to determine probability of offspring with a particular genotype Incomplete dominance – heterozygote has an intermediate phenotype btwn the homozygous dominant and homozygous recessive phenotypes o Ex: sickle-cell anemia SS = normal red blood cell shape ss = sickle-shaped red blood cell Ss = produce both normal and sickled RBC’s; resistance to malaria Multiple allelic inheritance – some genes have more than 2 forms; Blood type Genotype we inherit only 2 alleles O ii o Ex: ABO blood types A I I or I i I , I are co-dominant; i is recessive B I I or I i Sex-linked – genes inherited on sex chromosomes A B AB I I o X and Y are not homologous Y contains genes that determine maleness Y (15 genes) is 1/3 the size of X (2500 genes) X codes for additional non-sexual characteristics o Sex-linked genes – found only on X, not on Y Sex-linked recessive genes can’t be masked: no corresponding gene on Y X-linked genes never passed from father to son Polygenetic inheritance – multiple genes at diff. locations collectively control a single phenotype Early Development Pregnancy – fertilization until baby is born Conceptus – developing offspring o Preembryo – first 2 weeks following fertilization o Embryo –th-8 weeks of development o Fetus – 9 week to birth Gestation period – time during which development occurs o 280 days for humans o Start time: end of previous menstrual cycle Pregnancy begins prior to fertilization Includes follicular phase of menstrual cycle o Embryonic period o Fetal period Preembryonic development – events from fertilization to implantation Cleavage – period of rapid mitotic divisions; no growth in cell mass; daughter cells become smaller each division o Blastomeres – identical daughter cells produced during first 72 hours o Morula – 16+ cell stage Blastocyst production – fluid-filled hollow sphere of a single layer of 100+ cells o free from zona ellucid o Trophoblast – outer layer of blastocyst; later becomes the placenta o Inner cell mass – becomes embryonic disk + forms the embryo Implantation of blastocyst – about 6 days after fertilization o Window of implantation – endometrium must be ready Hormones (estrogen, progesterone) must be at appropriate levels Prepared endometrium – blastocyst implants high in the uterus Unprepared edometrium – blastocyst continues to move lower in uterus, implant where chemical enviro. is appropriate o Trophoblast adheres to & invades the endometrium Digests the uterine cells Blastocyst burrows into endometrium Surrounded by blood leaking from degraded endometrial blood vessels nutrients initially come from digested endometrial cells blastocyst is covered over and sealed off from uterine cavity its literally a parasite lmao o implantation – takes about 1 week th completes by 14 day after ovulation o implanted preembryo secretes hCG (human chorionic gonadotropin) hCG maintains the corpus luteum corpus luteum secretes progesterone pregnancy tests detect hCG levels Placenta – temporary organ of both maternal and fetal sources o Functions: Nutrition – starts to provide nutrients by 2 month Respiration Excretion Endocrine organ – takes over role of ovaries after 3 months hCG – (functions like LH) maintains corpus luteum hCS – breast development; levels increase through pregnancy progesterone – maintain the endometrium o levels peak at 3-4 weeks after fertilization o decline before increasing again up to parturition (birth) o second increase important to breast development estrogen – develop uterus to accommodate growing fetus o important for latter stages of breast development o Chorion – forms from trophoblastic tissue Connects fetal blood to maternal sources Materials diffuse through btwn two sources Embryonic development – blastocyst to gastrula Embryonic membranes o Amnion – transparent membranous sac filled with amnionic fluid around embryo amnionic fluid – initially derived from maternal blood; includes fetal urine Protects against physical trauma Prevents embryo parts from sticking together Allows musculoskeletal development o Yolk sac – hanging from embryo; forms part of digestive tract; produces first blood cells; source of primordial germ cells for gonads Primary source of nutrition in other animals Humans have the placenta o Allantois – becomes umbilical cord that links embryo w/ placenta Becomes part of urinary bladder o Chorion – encloses all other membranes and embryo Gastrulation – two-layered embryo becomes three-layered embryo o Creates basic structural framework of embryo for development of tissues and organs o Primary germ layers + their fates: Ectoderm – nervous system, skin epidermis Endoderm – epithelial linings of GI, respiratory and urogenital tracts Mesoderm – muscle, blood, bone, everything else Fetal development – weeks 9-40 Dimensional changes o start of fetal development: 30mm (1in) crown to rump length; 1 g weight o at birth: 360mm (14in) crown to rump; 2.7-4.1kg (6-10lb) weight; 550mm (22in) long 8 weeks = end of embryonic period o Head equal to body length o Large liver o Limbs present; webbed digits o Bones ossify o Cardiovascular system functional o All body systems present 9-12 weeks = 3 month o Body elongates; head still disproportionately large; brain enlargens o Skin epidermis forms o Crude facial features o Sex can be determined o Limbs well formed o Crown tothump length: 90mm (3.5in) 13-16 weeks = 4 month o Nervous system develops more Sensory organs differentiated Eyes blink Sucking motion of lips o Face looks human; body beginning to outgrow head o Crown tthrump length: 160mm (6in) 17-20 weeks = 5 month o Vernix caseosa – fatty secretions of sebaceous glands; covers the body o Lanugo – silk-like hair; covers the skin o Body is in fetal position; too large for space restrictions inside iterus o Limbs reach final proportions o Quickening – spontaneous muscular activity of fetus; mother starts to feel it o Crown to rump length: 190mm (8in) th th 21-30 weeks = 6 and 7 months o Substantial weight increase o Early birth survival is possible after week 27 Requires temperature regulation, ventilation o Eyes are open o Skin is red and wrinkled o Toenails, fingernails present o Lean, well-proportioned body o Limb bones begin to ossify o Crown to rump length: 290mm (12in) 30-40 weeks = 8 and 9 months o Skin is whitish pink o Fat in subcutaneous tissue o Crown to rump length: 360-400mm (14-16in) Cell potency Totipotent – single cell can divide and produce all the differentiated cells in an organism Pluripotent – cell can differentiate into any of the three germ layers Multipotent – potential to differentiate into multiple, but limited cell types Oligopotent – ability to differentiate into a few cell types Unipotent – can differentiate into only one cell type Embryonic stem cells – pluripotent cells derived from inner cell mass of blastocyst; can form every cell of the embryo proper Never collected from women Can’t be harvested after attachment to uterine wall o Consensus within scientific community: life begins at implantation Pre-blastocysts can be grown outside of uterus Zygote can develop in vitro until blastocyst stage o Blastocysts then frozen and stored indefinitely (supposedly) has to be stored in fertilized form: eggs can’t be frozen – less viable o Sperm can be harvested + frozen indefinitely Take home baby rate: 20% Cost of each attempt at in vitro fertilization: $25,000 Implant more blastocysts to reduce cost o Europe has a limit of 3 blastocysts for each reproductive attempt
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