BY1101 Introduction to Molecular and Cellular Biology . Tutorial for module BY1101: Embryology Joe Colgan ([email protected]). BY1101 Introduction to Molecular and Cellular Biology . Tutorial objectives. Describe the main events in embryogenesis
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Tutorial for module BY1101:
Joe Colgan ([email protected])
What is embryology?
-The science of the development of an organism from the fertilisation of the ovum to the fetus
What are gametes?
Haploid germ cells (sperm or egg (ovum))
What is a zygote?
Single diploid cell (earliest stage of embryonic development)
How do the gametes form?
Process of nuclear division in eukaryotic cells
Conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei
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
Nutrition, metabolism and development
Testes (Seminiforous tubule)
Location and penetration
Production of gametes
Female (Ovum) Male (sperm)
2. Acrosomal reaction
3. Interaction of gametes
4. Fusion of nuclei
Why is polyspermy a problem?
Fusion of haploid gametes (ovum + sperm) to produce a diploid zygote
A diploid zygote
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
Product of cleavage
Type of cleavage
Rapid cell division without cell growth
Blastula (Frog)/Blastoderm (Chick)
What is gastrulation?
Triploblastic – Three layers
Diploblastic – Two layers (Endo- and ectoderms only)
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
Two main cell types:
All cells that will contribute to the formation of the embryo will originate as epiblasts
Functional in the normal formation of the primitive streak
Site of involution during gastrulation
Formation of the embryonic germ layers
Gastrula (containing endoderm, mesoderm, ectoderm)
What is organogenesis?
How does it differ to gastrulation?
What are the steps involved in neurulation?
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 will become the brain and spinal chord in the embryo
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
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 four types of extra-embryonic membranes seen in the chick?
Form during organogenesis
Stage 5: Organogenesis
Formation of organs from the 3 germ layers formed during gastrulation
Neural crest cells
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
Campbell Chapter 47
Campbell Chapter 47