Lecture 2???? Animal Tissues and Development 1 Flashcards
How does Animal cloning take plaxe
Egg cell removed (oocyte donor)
Spindle including metaphase chromosomes are removed leaving enucleated egg
Udder cell removed (nuclear donor)
Udder cells placed in culture and grown to G1 phase
Transfer cell into enucleated egg
Egg and cell fused with electrical current
Embryo cultured for 7 days forming a blastocyst
Insert into surrogate
Birth of Dolly
What is microsatellite analysis
method used to examine variations in short, repetitive DNA sequences called microsatellites. These sequences, also known as simple sequence repeats (SSRs) or short tandem repeats (STRs), are found throughout the genome and exhibit natural variations in the number of repeats between individual
(slide 8)
How do you choose your animal model
Easy to maintain
Easy to breed
Cost
known genome sequence
Experimental advantages
Ethical considerations
Animal License
Genetics
Embryology
Genomics
What are the different types of Holoblastic cleavage (complete)
Radial
Spiral
Bilateral
Rotational (mammals)
Radial (displaced) (Amphibians)
What are the different types of Meroblastic cleavage (incomplete)
Bilateral
Discoidal
Superficial (insects)
What is the process for displaced radial cleavage in frogs
Frog eggs/embryos have an animal pole and an egg-rich vegetal pole. In some frog species the animal pole is darkly pigmented. Cell divisions occur without an increase in size of the blastula; this means that the cells become progressively smaller. The blastomeres (cells of the animal pole) divide more rapidly than the yolk cells (cells of the vegetal pole) and therefore become more numerous.
Slide 16 - I, II, III are cleavage vents
How does rotational cleavage occur in mice
Following fertilisation the pronuclei fuse. (one pronucleus contains the genetic material from the sperm and one pronucleus contains the genetic material from the ovum). The fertilised ooctye then divides forming two blastomeres, each containing identical genetic material. Division occurs by rotational cleavage meaning that there can be an odd number of blastomeres at certain times. Following the 8-cell stage compaction occurs whereby the cells clump together surrounded by the zona pellucida. At the 16-cell stage the blastula is now called a morula. The blastomeres of the morula continues to divide and will eventually form a blastocyst. A blastocyst consists of an inner cell mass surrounded by trophoblast cells and contains a fluid-filled cavity called a blastocoele. The blastocyst escapes from the surrounding zona pellucida by secreted enzymes which digest a hole in the lining of the zona pellucida; this process can be termed ‘hatching’.
(slide 18)
How does cleavage in insects take place eg. drosophila
Drosophila zygotes undergo rapid nuclear divisions without forming separate cells, this is called superficial cleavage. Some nuclei move to the posterior end to form ‘pole cells’ which will go on to form the germ cells (cells that make gametes). Following the 9th division the other nuclei move to the outer edges creating a syncytial blastoderm. Cell membranes then form around all the cells to create a cellular blastoderm. There are approximately 6000 cells at the end of this process.
What are the early developmental processes in a frog
Frog are vertebrates
Frogs are amphibians
Frogs undergo metamorphosis
Good model organism for experimental embryology
Xenopus leavis is a model organism which has been extensively studied
Vaguely look at slide 22
Where are frog eggs fertilised
Animal Pole, leads to cortical rotation
What is cortical rotation
30 degree shift on outer edge of cytoplasm, moving dark cytoplasm around and revealing grey crescent
Where is the dorsal lip
Just below the grey crescent
How does gastrulation in frogs occur
During gastrulation cells move into the embryo and generate the 3 germ layers; the ectoderm, mesoderm and endoderm. The animal pole cells at the dorsal lip of the blastopore begin to involute causing the future mesodermal and endodermal cells to be moved interiorly. The archenteron (primitive gut) is formed, displacing the blastocoel. The archenteron will eventually surround and enclose the yolk cells. The animal pole cells on the ventral side of the blastula meanwhile envelop the vegetal pole cells by epiboly, followed by some involution through the ventral lip of the blastopore. The head end (anterior end) will be formed at the leading edge of the mesoderm.
bottle cells move into cell, causing involution, dragging cells into inner lining of the embryo
Slide 25
What is epiboly
type of cell movement that occurs during gastrulation, a stage of embryonic development
thinning and spreading of a sheet or multi-layered group of cells, typically the ectoderm, over deeper layers of the embryo, often including the yolk. This movement helps to shape the basic body plan of the embryo and is observed in various organisms like zebrafish, amphibians, and tunicates
What are the different germ layers
Ectoderm (outer layer)
Mesoderm (middle layer)
Endoderm (internal layer)
How does Neurulation in frogs occur
Late gastrula contains notochord, raised neural folds appear either side of neural groove
