Karteikarten
Animal development
Karten in diesem Stapel (33)
- 1What is an animal model? Give key features.Any species that is widely studied
- Easy to maintain - Easy to breed
- Low cost - Experimental advantages
-Known genome - Space required
GENETIC MODELS = large array of mutants, large no. of offspring, short generation time
EMBRYOLOGICAL MODELS = robust, easily manipulated, external development
GENOMIC MODELS = relevance to human to genome, disease models, drug testing - 2Describe invertebrate models used.Caenorhabditis elgans - nematode worm
-very few cells
-Genetics simple
Drosophila melangaster - fruit fly
- simple geneticist
-lots of mutants - 3Describe vertebrate models used.DANIO RERIO - zebrafish, simple genetics, external development, clear embryo
XENOPUS LAEVIS - african clawed frog, external development, large eggs
GALLUS GALLUS DOMENSTICUS - chicken, experimental embryology
MUS MUSCULUS - mouse, gentic modification, mammal comparisons to humans - 4Explain xenopus egg.Unlike mammals, xenopus eggs have dark pigmented animal pole and egg rich vegetal plat which is used by the animal pole to obtain nutrients
- 5Explain cleavage in Xenopus.The first 3 cleavages are perpendicular to one another , the following divisions occur in a radial fashion. occur without increase in the size of the blastula which means cells become progressively smaller.
The cells of the animal pole blastomeres divide more rapidly than the cells of the vegetal pole yolk cells. - 6What is the grey crescent region.Sperm enters the egg somewhere on the animal pole. Rotation of the cortical cytoplasm takes place revealing grey crescent region opposite sperm entry point. Dorsal lip below grey crescent region.
- 7Explain the process of gastrulation in xenopus.During gastrulation cells move into the embryo and generate the 3 germ layers (ectoderm, mesoderm,endoderm)
-the animal pole cells at the dorsal lip begin to involte causing future medo and endodermal cells to be moved interiorly
-the archentron is formed displacing the blastocoel this eventually surround and encloses yolk cells
- the animal pole is on the ventral side of the blastula
-involution through lip of blastopore - 8Explain neurolation in xenopus.Process which produced the neural tube
-neural plate, cells start to thicken either side forming neural groove
- Folds appear either side of neural groove, these move together and forma a neural tube which dissociates.
= then organogenesis begins - 9Explain animal cloning.SOMATIC CELL NUCLEAR TRANSPLANT
- unfertilised egg exposed to uv radiation, injection of nucleus into enucleated egg = produces real clone
*cells taken from albino animal pole of xenopus
DIFFERENTIATED CELLS CAN ALSO BE USED
-injected nucleus taken from skin cells
=DNA can reprogrammed to allow development following differentiation. - 10What are transcription factors?Transcription factors are proteins that control transcription they bind to promoters,enhancers and polymerase.
=up rate or down rate gene regulation
=block or enhance transcription - 11What is signal transductiion?Signal transduction carries the signal from the cell membrane to the nucleus
-signalling centre secretes inductive signals that diffuse
- gradient of signal produced cells closest get highest dose
- signals bind to receptors which relayed into cell to nucleus - 12Explain how to find the signalling centre using xenopus.A ligature is placed around the fertilised egg restricting the nucleus to one side, cleavage occurs on the side containing the nucleus. At the 16 cell stage single cell crossed to other side of the ligature, tightened further and separated = halves develop
*if ligature cuts grey crescent both halfs make normal tadpoles
*if grey crescent on one side one half normal the other belly piece
=indicates grey crescent region is involved in signalling - 13Explain Spemann organiser graft.Cells taken from dorsal region of donor and implanted into ventral host region
= conjoined embryo - 14DEFINE: -cell fate -inductive signal -organiser graft -signal transductionCELL FATE - what a cell will become in the future
INDUCTIVE SIGNAL - extracellular signal causes cell to follow different fates
ORGANISER GRAFT - induces dorsal fate in region that should follow ventral fate
SIGNAL TRANSDUCTION - relays the message from extracellular signal from membrane to nucleus - 15Explain how to find gene responsible.Over express gene in embryos
= how does protein affect development - 16What is noggin?Noggin is a secreted signalling molecule that can promote dorsal structures
= no noggin produces belly piece
= normal noggin produces normal embryo
= high noggin produces head piece - 17Explain how to check where the gene is expressed.In situ hybridisation shows where mRNA for gene of interest is expressed
-RNA probe with DIG label
-Coloured precipitate - 18Outline drosophilia lifecycle.fertilised egg (cleavage) - syncitial blastoderm (gastrulation) - embryo (hatching) - 1st,2nd,3rd instar - pupa (hatching) - adult fly
*rapid life cycle takes 2 weeks - 19Explain superficial cleavage in drosophila.Drosophilia zygotes undergo rapid nuclear divisions without forming rapid cells
- genetic material in egg starts dividing no cells formed at this point
- 9th division nuclei move to edges creating syncitial blastoderm
- divisions continue, later specialised pole cells move to posterior end this will form germ cells
- after 11th division around 600 nuclei, mebranes form around them forming cellular blasoderm - 20Explain gastrulation in drosophilia.- Head region forms at the anterior end marked by cephalic fold
- Ventral furrow appears on ventral surface
- Cellular movements begin to occur, cells move inward at furrow via invagination forming ventral tube along whole length midline
-Tube dissociates and moves inside forming mesoderm
-Endoderm then forms, invaginations at two regions anterior and posterior end, these meet to form tube through entire embryo - 21Explain central nervous system formation in drosophilia.No neuralation occurs since flies are not vertebrates
- following invaginations of mesoderm ventral furrow closes
- Then ectodermal cells either side of the closed ventral furrow dissociate and start moving as individual cells into position between meso and ectoderm
=NEUROBLASTS - 22What is a genetic screen?A technique used to identify and study an interesting phenotype within mutated population.
*Generate mutants
*Identify mutated genes
*Find where genes expressed - 23Explain genetic screening of zebrafish.Mutagenesis of male fish. breed male and female populations, breed each f1 with wildtype +/+, f2 offspring interbred recessive phenotype observed
- 24List 7 homeotic mutations in drosophilia.LABIAL - (lab)
DEFORMED - (dfd)
SEX COMBS REDUCED - (scr)
ANTENNAPEDIA - (antp)
ULTRABITHORAX - (ubx)
ABDOMINAL A - (abdA)
ABDOMINAL B - (AbdB)
*order in which genes are found matches expression order - COLINEARITY* - 25Explain ultrabithorax null mutantADDITIONAL PAIR OF WINGS INSTEAD OF LEGS
- no ubx in thoraic segment 3
- no ubx in abdominal segments still normal - 26Explain antennapedia mutant.ADDITIONAL PAIR OF LEGS INSTEAD OF ANTENNAE
-antp in head region - 27Explain cleavage of zygote in mouse.-Following fertilisation the pronuclei fuse, the fertilised oocyte then divides forming two blastomeres each genetically identical
-Division occurs by rotational cleavage meaning there are an odd number of blastomere
-Following stage 8 compaction occurs and cells clump surrounded by zona pellucida
- Blasomeres continue to divide forming blastocyst - 28Explain implantation in mouse.--Prior to implantation the inner cell mass forms two layers = epiblast and hypoblast
-The primitive endoderm cells line the blastocoel forming yolk sac cavity
- The epiblast cells line the forming amniotic cavity
-The trophoblast cells the make contact with uterine wall continue to divide and ivade uterus to form syncytioblast - 29Explain gastrulation in mouse.Process that sets up 3 germ layers
-Signalling centre called the node signals for primitive streak to form which forms groove
-Epiblast cells dissociate and migrate through primitive groove and node invading endodermal cells and destroying them
-Movement of cells via ingresion forms 3 layes
- cells that moved through node become notochord
=ALL LAYERS FORMED FROM EPIBLAST - 30What do the 3 germ layers become?ECTODERM - epidermis,skin,brain and cns
MESODERM - muscle,bone, kidney, gonads,heart
ENDODERM - epithelium lining, liver,lung,pancreas - 31Explain neurolation in mouse.- Ectodermal cells start to thicken forming neural plate
-Neural groove forms along the midling and as cells thicken forms neural folds either side
-Neural folds rise and join together forming neural tube
-Neural tube dissociates from ectoderm - 32Explain transgenic miceMethod of over expressing gene
-fertilised zygote incubated in dish
-zygotes held still with pipette then dna inserted into male pronuclei
- zygote then transferred into oviduct - 33Explain targeted knockout in mice.-Obtain Es cells from inner cell mass
- make targeting vector, genetically modify stem cells
- inject these into blastocysst
-implant
=can observe phenotypic effects of gene
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- Biology (Semester one) (Cell and Molecular Biology) Karteikarten am Animal development, erstellt von Yasmin Beer am 23/01/2018.
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- Yasmin Beer
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