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Cell Biology > Animal tissues and development > Flashcards

Animal tissues and development Flashcards

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1
Q

Animal Cloning in Mammals

A
  • Used unfertilised egg.
  • Removed spindle to make vessel.
  • Cultured udder cells which had all genetic material.
  • Transferred nucleus of udder cell into empty site in vessel.
  • Embryo was then cultured and implanted into a sheep.
  • The lamb born was genetically identical to the nuclear donor.
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2
Q

Cloning taught us that…

A
  • DNA is not lost in specialised cells during development.
  • Gene expression must be regulated so that differentiation can occur.
  • DNA can be reprogrammed following differentiation, to form any cell type in the body.
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3
Q

Considerations for choosing an animal model

A
  • Easy to maintain?
  • Easy to breed?
  • Costs?
  • Experimental advantages?
  • Known genome sequence?
  • Ethical considerations?
  • Animal licence?
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4
Q

What makes a species good for studying genetics?

A
  • Large number of offspring
  • Short generation/gestation time
  • Large array of mutants available
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5
Q

What makes a species good for studying embryology?

A
  • Large number of embryos
  • External development
  • Robust, easy to manipulate embryos
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6
Q

What makes a species good for studying genomics?

A
  • Relevance to human genome
  • (gene conservation)
  • Disease models
  • Drug testing
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7
Q

Early developmental processes in the frog

A
  • Frogs are vertebrates.
  • Frogs are amphibians.
  • Frogs undergo metamorphosis.
  • Good model organism for experimental embryology
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8
Q

Poles in frogs eggs/embryos

A
  • animal pole
  • egg-rich vegetal pole.
  • In some frog species the animal pole is darkly pigmented.
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9
Q

Cell divisions occur without an increase in size of the blastula; this means that the cells become …

A

… progressively smaller.

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10
Q

Do cells of the yolk pole or animal pole divide more rapidly?

A

The blastomeres (cells of the animal pole) divide more rapidly than the yolk cells (cells of the vegetal pole) and therefore become more numerous.

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11
Q

Where does the sperm enter

A
  • The sperm enters somewhere at the animal pole.
  • Rotation of the cortical cytoplasm then takes place revealing a grey crescent region opposite the sperm entry point.
  • The dorsal lip is just below this grey crescent region.
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12
Q

Gastrulation in frogs

A
  • Forms the multi-layered embryo.
  • 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
  • The archenteron (primitive gut) is formed, displacing the blastocoel.
  • 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
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13
Q

Involute

A

Causes the future mesodermal and endodermal cells to be moved interiorly.

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14
Q

Neurulation

A
  • Occurs after gastrulation and forms the closed neural tube.
  • Raised neural folds appear either side of a neural groove.
  • The folds move together to form a closed neural tube.
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15
Q

Cell divisions in frog embryos occur without an increase in size of the …

A

… blastula. This means that cells get progressively smaller.

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16
Q

Cleavage in mammals can be …, in contrast to the … cleavage of frogs.

A

Asynchronous
Regular

17
Q
A
18
Q

Superficial cleavage

A

As in drosophilia zygotes (insects)
Rapid nuclear divisions without forming separate cells.

19
Q

Invagination

A

When cells around the outside of an embryo move inside the embryo by forming a pocket of cells into the embryo.

20
Q

Involution

A

When cells move inside the embryo as a sheet on the inside edge.

21
Q

Ingression

A

When you have a sheet of cells, some of which lose their connectivity and move into the embryo as single cells.

22
Q

Delamination

A

When a whole sheet enters the embryo, like ingression.

23
Q

Epiboly

A

Where cells spread and cover the entire early embryo.

24
Q

Genes wash over the embryo in a gradient. Because of this, …

A

… different genes are turned on and off. This causes body plan regions within the embryo.

25
Q

Forward genetics

A
  1. Start with random mutation
  2. Find phenotype
  3. Find gene
26
Q

Reverse genetics

A
  1. Start with gene
  2. Remove gene
  3. Look at phenotype
27
Q

Genetic screens

A
  • Forward genetics
  • Identify and study a phenotype within a mutated population
    1. Generate random mutants
    2. Oserve phenotype of random mutants
    3. Identify the gene/s that are mutated
28
Q
  1. Generate random mutants

Genetic screeens

A
  • Male fish are mutagenized with chemical agent.
  • Allow males and females to reproduce producing F1 (+/-) and (+/+)
  • Each F1 is bred with wild-type (+/+) partner (produces F2 families)
  • F2 inbred to get F3 (can now see some (-/-) phenotypes, 1/16 of them).
29
Q
  1. Identify the gene/s that are mutated

Genetic screens

A

In situ hybridisation can be used – you can see the RNA product of a gene and find where it was expressed.
* Embryos fixed and mixed with RNA tag and antibodies that are labelled with an enzyme.
* Embryos are washed and the substrate reacts with the enzyme.

30
Q

Genetic engineering

A
  • Reverse genetics
  • A technique used to modify gene expression within an organism
  • Includes transgenesis and targeted knockouts.
31
Q

Transgenesis

A
  • Addition of a transgene
  • Plasmid DNA with gene of interest and a detection marker
  • The location where the gene is added within the genome is random
  • Plasmid DNA is inserted into fertilised zygotes before being replanted into a host.
32
Q

Targeted knockouts

A
  1. Generate a targeting vector
  2. Obtain embryonic stem cells
  3. Genetically modify ES cells
  4. Inject modified ES cells into blastocyte - recombinant
  5. Implant recombinant embryos into pseudopregnant surrogates
  6. Screen for chimeric mice
  7. Breed the chimeric mice
33
Q

Generate a targeting vector

Targeted knockouts

A

Disrupted gene of interest means no mRNA can be produced

34
Q

Obtain embryonic stem cells

Targeted knockouts

A

Requires undifferentiated ES cellls growing in culture

35
Q

Genetically modify ES cells

Targeted knockouts

A

Homologous recombination can cause swapping out of host DNA for added DNA

36
Q

Chimeric mice

A

Have a mixture of normal cells and targeted cellls.
Often coat colour markers are used.

Cell Biology (16 decks)

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