Lecture 21b Flashcards
What is the null allele for the Antp gene?
It is embryonic lethal, meaning that the fly cannot live.
A gain of function mutation that causes the Antp gene to be expressed further anteriorly results in what?
Results in legs growing where there should be antennas.
What does the Ubx gene specify?
Specifies the segment behind the one with the wings and is expressed all the way to the anterior tip.
Basically, it specifies what is behind the wings, not the actual wings themselves.
What does a mutation in Ubx result in?
A second segment with wings giving the fly an extra set of wings.
Is the Ubx gene an essential gene?
No cuz an extra set of wings can still allow the fly to live healthily.
What do Homeotic genes encode?
Encode for transcription factors that active sets of genes.
Where are DNA-binding sites found for the DNA-binding domain?
Within enhancers
Name the 4 vertebrate species that are studied for development.
Chicken, african clawed toad (Xenopus laevis), Zebrafish (Brachydanio rerio), and mouse.
What do chicken embryos resemble? How are they different?
Resemble mouse and human embryos, but they develop in an egg rather than inside the mother.
In chicken, where does the embryo lay?
On top of the yolk
How can chicken embryo development be observed?
Egg shell can be removed and development videotaped all the way to hatching.
How many days does it take for chicken to go from fertilization to hatching of the egg?
21 days
How could we manipulate chicken embryos to make regions untranslatable?
siRNA, antisense RNA, or morphilinos can be electroporated into the embryos at one side of the embryo.
What are Morphilinos?
They are like antisense RNA but chemically more stable (cannot be degraded because they aren’t RNA). They make an area untranslatable.
How could we manipulate chicken embryos to express a gene of interest?
Plasmids to express a gene of interest can be electroporated into the embryos.
Originally, in hospitals, what were African Clawed Frogs (Xenopus) used for?
Used in pregnancy tests
How were African Clawed Frogs (Xenopus) used for pregnancy tests?
Urine from pregnant women contain chorionic gonadotropin. The urine was injected into female Xenopus. If the urine was from a pregnant woman, Xenopus would lay eggs the next day.
Nowadays, how do we detect pregnancy?
An antibody to detect human chorionic gonadotropin is used to detect pregnancy.
After African Clawed Frogs (Xenopus) were not needed for pregnancy, why did scientists keep working with them?
Hospitals had colonies of these animals and the eggs were nice and large. They could injected human chorionic gonadotropic, fertilize the eggs, and observe the frogs lay them.
How big are African Clawed Frogs (Xenopus) eggs?
HUGE MOTHERFUCKERS!
1 mm in diameter
In relation to African Clawed Frogs (Xenopus), what is injected at various stages using thin glass needles? When is this done in the embryo cycle?
Embyro is injected.
Can be in 2-cell embryo (to produce a control side) or later in like the 32-cell stage (popular).
How did African Clawed Frogs (Xenopus) become an invasive species?
Live fertilized eggs went down sinks into sewage systems and now a bunch of universities have Xenopus everywhere where the climate is appropriate.
Why can African Clawed Frogs (Xenopus) easily become a harmful invasive species?
They are voracious predators and easily adapt to many habitats.
They have been shown to devastate native populations of frogs and other creatures by eating their young.
Why are African Clawed Frogs (Xenopus) important carriers?
They carried B. dendrobatidis, which is a fungus that has resulted in a drastic decline in amphibian populations around the world. The fungus does not affect the African Clawed Frogs (Xenopus), so it is a good carrier.
T/F: Zebrafish take a long time to produce a large number of externally developing diploid embryos.
False! They can quickly produce a large number of externally developing diploid embryos.
What allows for real-time imaging of all developmental stages in Zebrafish?
The transparency of embryos and larvae.
T/F: Zebrafish have large embryos.
True!
T/F: We can mutagenize and then screen many zebrafish embryos for the desired mutant phenotype.
True!
T/F: Zebrafish can be inbred.
False! They would not be alive if they were inbred.
