Presentation is loading. Please wait.

Presentation is loading. Please wait.

Tutorial for module BY1101: Embryology Joe Colgan BY1101 Introduction to Molecular and Cellular Biology.

Similar presentations


Presentation on theme: "Tutorial for module BY1101: Embryology Joe Colgan BY1101 Introduction to Molecular and Cellular Biology."— Presentation transcript:

1 Tutorial for module BY1101: Embryology Joe Colgan BY1101 Introduction to Molecular and Cellular Biology

2 Tutorial objectives Describe the main events in embryogenesis Compare and contrast the events between different organisms BY1101 Introduction to Molecular and Cellular Biology

3 Embryology What is embryology? -The science of the development of an organism from the fertilisation of the ovum to the fetus BY1101 Introduction to Molecular and Cellular Biology

4 Sexual reproduction BY1101 Introduction to Molecular and Cellular Biology What are gametes? Haploid germ cells (sperm or egg (ovum)) What is a zygote? Single diploid cell (earliest stage of embryonic development)

5 BY1101 Introduction to Molecular and Cellular Biology Mitosis: Process of nuclear division in eukaryotic cells Conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei Meiosis: Modified form of cell division in sexually reproducing organisms Involves two round of cell division but only one round of DNA replication Produces cells with half the numbers of chromosome sets as the original cell How do the gametes form?

6 What differences are there in the gametes? BY1101 Introduction to Molecular and Cellular Biology Spermatogenesis Product: Sperm Location: Testes (Seminiforous tubule) Specialised function: Location and penetration Oogenesis Product: Ovum (Egg) Location: Ovary Specialised function: Nutrition, metabolism and development

7 Stage 1: Gametogenesis Gametogenesis Production of gametes Female (Ovum) Male (sperm) Haploid gametes Stage 1: Event Product BY1101 Introduction to Molecular and Cellular Biology

8 What are the major events in fertilisation? BY1101 Introduction to Molecular and Cellular Biology 1. Contact 2. Acrosomal reaction 3. Interaction of gametes 4. Fusion of nuclei

9 Fertilisation BY1101 Introduction to Molecular and Cellular Biology

10 What are the two defences to polyspermy? Fast block against polyspermy Acrosomal reaction -> Depolarisation Slow block against polyspermy Cortical reaction -> Fertilization envelope BY1101 Introduction to Molecular and Cellular Biology Why is polyspermy a problem?

11 Stage 2: Fertilisation BY1101 Introduction to Molecular and Cellular Biology Fertilisation Fusion of haploid gametes (ovum + sperm) to produce a diploid zygote A diploid zygote Stage 2: Event Product

12 What are the major events in cleavage? Rapid cell division of zygote into blastomeres 5-7 divisions forms a ball of cells: Morula Fluid filled cavity is the blastocoel Surrounding hollow ball of cells are the blastula BY1101 Introduction to Molecular and Cellular Biology MorulaBlastulaBlastocoel Fertilised zygote Early division Early cleavage Late cleavage Blastomeres

13 What is a major factor that influences cleavage? Yolk proteins – importance constituent of developing embryos Proportion varies across species Yolk affects cleavage Greater aggregation at vegetal pole BY1101 Introduction to Molecular and Cellular Biology Animal pole Vegetal pole

14 What are the major events in cleavage formation in the frog? BY1101 Introduction to Molecular and Cellular Biology Animal pole Vegetal pole

15 Is cleavage different in the chick? BY1101 Introduction to Molecular and Cellular Biology All the cytoplasm of the cell is contained in a small disk Cleavage planes cannot penetrate the yolk Only cytoplasm at the animal pole is cleaved Cleavage produces a small cap of cells – blastoderm Blastoderm is the chick equivalent of blastula

16 Holoblastic (Complete) Meroblastic (Partial) What are the two types of cleavage? BY1101 Introduction to Molecular and Cellular Biology

17 Cleavage (Comparative) BY1101 Introduction to Molecular and Cellular Biology Blastula Blastoderm Holoblastic Meroblastic Product of cleavage Type of cleavage Sea urchinFrogChick Model organism

18 BY1101 Introduction to Molecular and Cellular Biology Cleavage Rapid cell division without cell growth Blastula (Frog)/Blastoderm (Chick) Stage 3: Event Product Stage 3: Cleavage

19 Next step: Gastrulation A series of cell and tissue movements in which the blastula- stage embryo folds inward, producing a 3 layered embryo, the gastrula BY1101 Introduction to Molecular and Cellular Biology Triploblastic – Three layers Diploblastic – Two layers (Endo- and ectoderms only) What is gastrulation?

20 What are the three embryonic germ layers? BY1101 Introduction to Molecular and Cellular Biology

21 What are the main events of gastrulation in the sea urchin? BY1101 Introduction to Molecular and Cellular Biology

22 What differences occur in gastrulation of the frog? 1. Cells begin to invaginate at the dorsal lip of the blastopore 2. Involution – Cells move over the dorsal lip and begin to move into the blastopore 3. Blastocoel collapses and is replaced by the archenteron

23 BY1101 Introduction to Molecular and Cellular Biology Two main cell types: Epiblasts All cells that will contribute to the formation of the embryo will originate as epiblasts Hypoblasts Functional in the normal formation of the primitive streak What differences occur in gastrulation of the chick?

24 Gastrulation (Comparative) BY1101 Introduction to Molecular and Cellular Biology Blastopore Primitive streakSite of involution during gastrulation Sea urchinFrogChick Model organism

25 BY1101 Introduction to Molecular and Cellular Biology Gastrulation Formation of the embryonic germ layers Gastrula (containing endoderm, mesoderm, ectoderm) Stage 4: Event Product Stage 4: Gastrulation

26 The stage at which the embryonic germ layers localise into the basic structure of organs BY1101 Introduction to Molecular and Cellular Biology What is organogenesis? How does it differ to gastrulation?

27 Case study: Neurulation BY1101 Introduction to Molecular and Cellular Biology First steps in brain and spinal cord Mesodermal cells form the notochord Ectodermal cells above form the neural plate Neural plate folds inwards to form the neural tube Neural tube will become the brain and spinal chord in the embryo What are the steps involved in neurulation?

28 BY1101 Introduction to Molecular and Cellular Biology Somites Location: Groups of cells located in strips of mesoderm lateral to the notochord form blocks Function: Segmentation of the body structure, vertebrae What are the two sets of specialised cells associated with neurulation? Neural crest cells Location: Borders from where the notochord pinches off from the ectoderm Function: Formation of peripheral nerves, teeth and skull bones

29 BY1101 Introduction to Molecular and Cellular Biology What are the four types of extra-embryonic membranes seen in the chick? Amnion- Fluid filled sac Bathes the embryo Chorion- Outer membrane Gas exchange Yolk sac- Encloses the yolk Blood vessels develop to bring nutrients Allantois- Waste disposal sac Also gas exchange Form during organogenesis - Endoderm - Mesoderm - Ectoderm

30 BY1101 Introduction to Molecular and Cellular Biology Organogenesis Formation of organs from the 3 germ layers formed during gastrulation Internal organs Stage 5: Event Product Stage 5: Organogenesis

31 BY1101 Introduction to Molecular and Cellular Biology Summary

32 Exam Questions BY1101 Introduction to Molecular and Cellular Biology Notochord Neural plate Neural folds Neural tube Neural crest cells

33 Exam Questions BY1101 Introduction to Molecular and Cellular Biology Gametogenesis Fertilisation Cleavage Gastrulation Organogenesis

34 Exam Questions BY1101 Introduction to Molecular and Cellular Biology Amnion Chorion Yolk sac Allantois

35 Exam Questions BY1101 Introduction to Molecular and Cellular Biology 2010/ /2009

36 Essay practice BY1101 Introduction to Molecular and Cellular Biology Q. 5 What is organogenesis? Describe the importance of neurulation in establishing the body plan of the embryo. Write an introductory paragraph to the essay above. - Introduction should address the question being asked - Should be concise (max. 1 paragraph) Using bullet points, outline the main concepts you would have in your main text body to support your answer - Including labelled drawings to support your answer are recommended Write a concluding paragraph - Should readdress the question - Summarise the main points from your essay - Be concise (max. 1 paragraph) - Should not include any new information

37 BY1101 Introduction to Molecular and Cellular Biology Next week: Developmental genetics Further reading: Campbell Chapter 47

38 BY1101 Introduction to Molecular and Cellular Biology Questions Further reading: Campbell Chapter 47


Download ppt "Tutorial for module BY1101: Embryology Joe Colgan BY1101 Introduction to Molecular and Cellular Biology."

Similar presentations


Ads by Google