BSB Issues 150, Week 4
BSB Issues 150, Week 4 01:119:150
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This 3 page Class Notes was uploaded by Wendy Liu on Thursday October 6, 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 46 views. For similar materials see Biology, Society, and Biomedical Issues in Biological Sciences at Rutgers University.
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Date Created: 10/06/16
Week 4: Embryonic Stem Cell Research 3 October 2016, 6 October 2016 Biology, Society, and Biomedical Issues Professor Uzwiak Wendy Liu Basic Cell Cycle (see week 3 notes for more detail) Interphase o G 1 growth phase o S – synthesis phase: duplicate DNA so that now there are 4 sets of DNA in total: 2 maternal (identical to each other) and 2 paternal (identical to each other) o G 2 more growth Mitotic phase o Mitosis – division of DNA Prophase Metaphase Anaphase Telophase o Cytokinesis – division of cell body Diploid – 2n – cell that contains sets of DNA from 2 different sources (maternal and paternal); somatic cells (i.e. most cells) in the body are diploid Haploid – n – cell that contains DNA from 1 source (doesn’t have to be just 1 set: can be 2 sets of identical DNA); germ cells in the body are haploid Meiosis – process of cell division that produces gametes reductive division: reduce # of copies of DNA by half Meiosis I: 4N2n 2N1n o 4 sets of DNA from 2 sources, becomes 2 sets of DNA from 1 source Meiosis II: 2N1n 1N1n o 2 sets of DNA from 1 source, becomes 1 set of DNA from 1 source Meiosis results in 4 haploid daughter cells that are each genetically unique from one another and the mother cell Oogenesis: form of meiosis that produces eggs and polar bodies Meiosis I: primary oocyte secondary oocyte & polar body o Polar body – small haploid cell that disintegrates + isn’t fertilized by sperm Division is uneven, in that most of the cytoplasm + other cellular materials go into the secondary oocyte Polar body is basically just DNA + membrane Meiosis II: secondary oocyte egg + polar body o takes place only if fertilization occurs Timeline of Oogenesis Embryo: while female is in the embryonic stage o Primary oocytes start meiosis I, but stop at prophase o “eggs” within ovaries form before the female is born Menstrual cycle o Continue meiosis I o primary oocyte secondary oocyte + polar body Fertilization o Continue to meiosis II & finish o secondary oocyte egg + polar body Ovulation (of female humans during years of reproductive viability) Ovaries hold primary oocytes, not eggs Ovaries release secondary oocytes, not eggs 4-5 day fertile window o After release, secondary oocyte stays viable for 24 hours o Sperm can stay viable within female reproductive tract for 1 week o 3-4 days before ovulation: cervical wall (entrance into uterus) becomes less viscous so sperm can enter Fertilization: Fertilization occurs in fallopian tubes o Male who produces < 50 mil. sperm is considered sterile o Average sperm count in ejaculate = 250 mil. sperm Egg takes 8-10 days to travel down fallopian tubes down into uterus o Menstruation occurs ~14 days after ovulation Preembryonic development Zygote housed in many layers o Outer layer is hard o Cells go through rapid cell division (cleavage) and get smaller (no cell growth in between) Blastomeres – each cell formed by cleavage of the fertilized ovum Embryonic disk/inner cell mass – single layer of cells in the shape of a ring (hollow in he inside) o Forms after repetitive cleavage o Becomes the human Trophoblast – surrounds inner cell mass o Becomes the placenta Blastocyst – entire unit of the trophoblast + inner cell mass o Not an embryo: has not implanted into the endometrium yet Cell potency Totipotent – each cell can form entire human o The first 4 blastomeres are totipotent o Full human will form even if 1 is removed Pluripotent – each cell can differentiate into many types of cells, but not all; one cell cannot make up entire human o The first 8 cells following cleavage after fertilization are pluripotent o Human won’t form if 1 cell is removed: rest will die Hereditary Fraternal twins – fraternal twins can run in the family history Mother’s levels of FSH stay high for longer than normal Follicle stimulating hormone (FSH) – matures a follicle containing a secondary oocyte in ovaries Excess FSH = multiple follicles being stimulated = multiple oocytes released Barriers in reproduction(f) Can’t make eggs, but uterus can bear offspring More infertile women today than in the past o More women are delaying reproduction due to shift in focus onto career o Oocytes become less viable as time passes by IVF-ET – in vitro fertilization embryo transfer Egg + sperm blastocyst Takes place in vitro (outside of body/in lab) Differentiation – elaborate process of a general cell becoming a specific, distinguished, specialized cell Cloned offspring die earlier than original DNA donor Template DNA is old and has already been damaged The damage amplifies in the clone Organ – combination of 2+ tissues 4 types of tissue 1. Muscle 2. Epithelial 3. Connective 4. nervous Goal of nondividing cell: Maintain its own existence Contribute to the organism DNA – contains genetic info Exons – expression: DNA regions that are expressed Introns – intervening: DNA regions not expressed ~28,000 genes in human genome Bones: mostly calcified collagen (protein) Mass of bone is 95% collagen Oxytocin – protein based hormone Stimulates milk secretion Positive feedback loop: uterine contractions during labor
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