Bioe 20B W5D1 Development Notes PDF

REMINDERS ANNOUNCEMENTS 1. Today: Development; Thursday: Start Plants Tuesday, 10/29/24 2. Due Sunday: HW 5, Quiz 5, Figure Summary 3. Content videos are mandatory; 75% must be completed to pass the class Week 5, Day 1 Development Part 2 TODAY’S...

REMINDERS ANNOUNCEMENTS 1. Today: Development; Thursday: Start Plants Tuesday, 10/29/24 2. Due Sunday: HW 5, Quiz 5, Figure Summary 3. Content videos are mandatory; 75% must be completed to pass the class Week 5, Day 1 Development Part 2 TODAY’S AGENDA (8-9:35AM) Development Part 2 5 min break Kahoot: Development Development II  Learning Goals for Today 1 First steps after fertilization 2 Patterns of early cell divisions 3 Gastrulation in Mammals & Birds & Formation of the Germ Layers 4 Organogenesis - How do organs develop? 5 Stages of human development Gametogenesis - making of eggs & sperm (read CH 43.2) 1n 1n Fertilization – formation of zygote (2n) Early cleavage – pattern of cell division IVF is usually done Blastocyst – early structure in fallopian tube 32-cell stage Implantation – occurs on day 6-7 In the uterus Pregnancy can be detected with blood test after 9-14 days PC Gastrulation – germ layer formation 3-layers: (endoderm, mesoderm, ectoderm) (formation of nervous system) Organogenesis & neurulation – formation of organs and organ systems REVIEW: Fertilization How does fertilization activate development? When one sperm successfully enters, other sperm are blocked off Changes in ion fluxes across egg membrane, pH of egg cytoplasm Increased egg metabolism/protein synthesis Initiates rapid series of cell divisions What do the egg and sperm contribute, respectively? Egg = has cytoplasm with organelles, Sperm = brings other set of chromosomes nutrients, transcription factors, mRNAS and the centriole REVIEW: FERTILIZATION Label as many parts as you can Where does fertilization and implantation happen? Day 1 = Fertilization happens in the fallopian tube (oviduct) Days 2-4 = Cleavage occurs as zygote travels down to uterus Day 6 = Blastocyst arrives in uterus, trophoblast adheres to uterus lining REVIEW: FERTILIZATION (Blastocyst) Label as many parts as you can Fallopian tube Where does fertilization and Fallopian tube implantation happen? Uterine wall (endometrium) Uterus Day 1 = Fertilization happens in the fallopian tube (oviduct) Days 2-4 = Cleavage occurs as (Releases zygote travels down to uterus (Seal off one egg (Where sperm fallopian tube) per and egg meet) Day 6 = Blastocyst arrives in uterus, month) trophoblast adheres to uterus lining Pregnancy tests detect = human choriandic gonandotropin (HCG) IUDs implant in uterus = 2 types: copper and hormone REVIEW: FERTILIZATION ON YOUR BOARDS: Draw or describe development from fertilization to implantation 1. Ovary releases egg à 2. Sperm joins with egg in fallopian tube and becomes a zygote à 3. Cell division occurs until 32-cell stage (blastocyst) à 4. Blastocyst enters uterus and trophoblast implants into uterine wall (endometrium) REVIEW: FERTILIZATION What happens if implantation occurs too early? Ectopic pregnancy = extrauterine pregnancy (i.e. tubule pregnancy) life-threatening to mother What can cause this? Early implantation is prevented Fibrosis/fibroids in fallopian by zona pellucida protein tubes can slow down membrane developing zygote so that it implants outside of uterus Blastocyst “hatches” when it reaches the uterus REVIEW: FERTILIZATION Egg is viable for 1 day Viability of both Why is the fertile sperm and egg are window ~5 days? Sperm is viable for up to 5 days put to the test! à Sperm must travel from vagina to fallopian tube à Egg must travel from fallopian tube to uterus (evolutionarily advantageous to select best sperm)  (Same DNA) Identical = one egg and one sperm Most likely, How are twins formed? (Similar DNA as siblings) Fraternal = 2 eggs and 2 sperm most safe Semi-identical = 1 egg, 2 sperm What determines different Depends on types of identical twins? when split occurs Two placenta Two amniotic sacs What factors increase risk for fraternal twins? Woman over 35 with 4 kids 3x more One placenta Two amniotic sacs likely to have fraternal twins Risk of African American 1 in 79 entanglement Caucasian 1 in 100 in each other’s Asian 1 in 155 umbilical cords First month after getting off pill One placenta One amniotic sac Mother’s family history Least likely, By Kevin Dufendach - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=5324027 most risky  What is the take home Just for fun: Ovulation message of this graph? Starting with puberty and lasting until menopause, one egg is chosen and released each month during ovulation  Learning Goals for Today 1 First steps after fertilization 2 Patterns of early cell divisions 3 Gastrulation in Mammals & Birds & Formation of the Germ Layers 4 Organogenesis - How do organs develop? 5 Stages of human development  What type of cell cleavage is this an example of? A.Complete B.Incomplete Cell cleavage allows fertilized C.Superficial egg to rapidly divide into a D.Syncytial multicellular embryo  Why is superficial Complete Cleavage cleavage beneficial to morphogen gradients? (bicoid, nanos, hunchback) Incomplete Cleavage Not hindered by multiple plasma membranes Superficial Cleavage REVIEW: Types of Cell Cleavage Fill out the table below… Complete Cleavage Incomplete Cleavage Superficial Cleavage Definition Cleavage furrows divide Cleavage furrows do not Mitosis occurs without egg completely divide all of the egg cell division (single cell has many nuclei) Drawing embryo syncytium yolk (nutrients) Found in which species? amphibians, mammals Fishes, birds, other reptiles Insects (frog) (fruit fly) Yolk present? Little or no yolk Lots of yolk Core of yolk Patterns of cell cleavage What are the characteristics of mammalian cleavage? - Cell divisions are slow - Cell division is asynchronous - Rotational (Complete) Cleavage Patterns of cell cleavage After 32 cell stage Cells become the Blastocyst Trophoblast - secretes fluid & forms the blastocoel Inner Cell Mass - becomes embryo (origin of ESCs)  Patterns of cell cleavage What happens during implantation? Epiblast becomes the animal – will undergo gastrulation next 1. Trophoblast cells secretes adhesion molecules and (“bag of waters”) proteases to allow blastocyst to burrow into endometrium (uterine wall) 2. Trophoblast cells send out chorionic villi to increase SA of contact with mother’s blood stream 3. Inner cell mass divides into two embryonic tissues (hypoblast -EES and epiblast -ES) 4. Epiblast splits to form the amniotic cavity  Learning Goals for Today 1 First steps after fertilization 2 Patterns of early cell divisions 3 Gastrulation in Mammals & Birds & Formation of the Germ Layers 4 Organogenesis - How do organs develop? 5 Stages of human development The developmental biologist Lewis Wolpert once said, “It is not birth, marriage, or death, but gastrulation which is the most important time in your life.” Do you agree or disagree and why? REVIEW: Gastrulation How does the blastocoel facilitate gastrulation? Fluid-filled space that allows for cell movement to form respective germ layers  Learning Goals for Today 1 First steps after fertilization 2 Patterns of early cell divisions 3 Gastrulation in Mammals & Birds & Formation of the Germ Layers 4 Organogenesis - How do organs develop? 5 Stages of human development REVIEW: Organogenesis Which germ layers will give rise to what? REVIEW: Organogenesis Which germ layers will give rise to what? REVIEW: Organogenesis Fill out the table and label the figure below… Endoderm Mesoderm Ectoderm Definition Innermost germ layer Middle germ layer Outermost germ layer Letter in C A B Figure Skeleton, circulatory system, Skin, sense organs, Digestive and Gives rise to? muscles, excretory system, and nervous system respiratory systems most of reproductive system A B C What contributes to spinal cord? Neural tube Neurulation Formation of nervous system What contributes to vertebrae? Notochord How is neurulation an example of induction? Cell-cell signaling in neural plate leads to formation of neural tube (Spinal cord) (Vertebrae) (Gives rise to CNS (Gives rise to PNS) à spinal cord and What is spina bifida? brain) Neural tube (spinal cord) defect from lack of folic acid REVIEW: Gastrulation vs. Neurulation What is gastrulation? Stage early in development characterized by many cell movements à Formation of the three germ layers What has been “accomplished” when gastrulation is complete? 1) 3 germ layers – endoderm, ectoderm, mesoderm 2) Body axes – dorsal/ventral and anterior/posterior What is neurulation? Formation of the nervous system à result of cell-to-cell signaling/induction What has been “accomplished” when neurulation is complete? Beginning of central nervous system (brain + spinal cord) derived from neural tube, as well as peripheral nervous system derived from neural crest cells  5-min Break! Attendance Time Scan the QR code or go to https://tinyurl.com/W5D1gastrulation to answer the following question: 1) What is gastrulation? (This will be used for taking attendance today.)  Learning Goals for Today 1 First steps after fertilization 2 Patterns of early cell divisions 3 Gastrulation in Mammals & Birds & Formation of the Germ Layers 4 Organogenesis - How do organs develop? 5 Stages of human development REVIEW: Placenta Capillaries allow for gas exchange of O2 and CO2 Does baby blood and mother’s blood come into contact? àNot directly because there is always a cell membrane between The placenta is the only organ made from two individuals and the only organ we make and discard! REVIEW: Placenta Weighs 2-3 lbs at full term Starts to break down/calcify around 40-43 weeks Mother needs to be induced after 2 weeks because of this!  Key Concepts for: Development What did we learn? Describe the difference between determination and differentiation Explain and give examples of differential gene expression (DGE) Describe cytoplasmic segregation and induction and give explanations for how these can lead to DGE Draw a graphical representation of how a morphogen gradient works Describe morphogen gradient of AP axis development in Drosophila Correctly predict outcome of various mutants in AP development in Drosophila Define hox genes and what they do REVIEW: Development Time to review development!