Mod 7- 303

Question 1

Xenopus laevis

Xenopus and other amphibians are? because of which ?

Xenopus is ?ploid i.e. no genetics (CRISPR/Cas9 genome editing may change this?)

molecular techniques ? why means remains a powerful model

Answer 1

Xenopus and other amphibians are NOT genetic models. Cell and Tissue transplantation and grafting experiments are easily done.

Xenopus is tetraploid i.e. no genetics (CRISPR/Cas9 genome editing may change this?)

molecular techniques (expression of dominant negative proteins, in situ hybridization, anti-sense oligo’s, chromatin IP) means remains a powerful model

Question 2

Xenopus is a genus of African frogs that are commonly known as the ?

Two species of Xenopus are regularly used by biologists, ? and ? Fully aquatic - easy to keep (in fish tanks).

Frog eggs are large (~?diameter), produced in large quantities, and easy to ?

Egg production can be stimulated by? (HcG). In the 1930’s Xenopus used to be a simple ?. Urine of a pregnant woman contains ?, which stimulates ?

Answer 2

Xenopus is a genus of African frogs that are commonly known as the African clawed toed frog.

Two species of Xenopus are regularly used by biologists, Xenopus laevis and Xenopus tropicalis. Fully aquatic - easy to keep (in fish tanks).

Frog eggs are large (~1.2mm diameter), produced in large quantities, and easy to manipulate.

Egg production can be stimulated by injection of human chorionic gonadotropin (HcG). In the 1930’s Xenopus used to be a simple pregnancy test. Urine of a pregnant woman contains HcG, which stimulates Xenopus ovulation.

Question 3

Xenopus laevis

Frog embryos develop externally , allowing experiments to be performed when?

Rapid embryo growth and development means that ?

Very well characterized ?

Answer 3

Frog embryos develop externally, allowing experiments to be performed prior to, or directly following fertilization.
Rapid embryo growth and development means that within a couple of days, a tadpole has a fully functional set of organs
Very well characterized morphology, large reagent base

Question 4

Amphibian development: the frog – Xenopus laevis

mature Xenopus egg distinct?
? animal region
? vegetal region
egg is enclosed in a ?, embedded in a ?
? is completed upon fertilization
fertilization is?

Answer 4

mature Xenopus egg has distinct polarity
dark pigmented animal region
pale yolky heavier vegetal region
egg is enclosed in a protective vitelline membrane, embedded in a gelatinous coat
second meiotic division is completed upon fertilization
fertilization one sperm enters eggs in the animal region

Question 4

Animal hemisphere:

Answer 4

The non-yolk-containing (upper) half of the amphibian egg. During embryogenesis, cells in the animal hemisphere divide rapidly and become actively mobile (“animated”).

Question 5

Vegetal hemisphere: ?

Answer 5

Vegetal hemisphere: The bottom portion of the amphibian egg, containing yolk, which serves as food for the developing embryo. The yolk-filled cells are divide more slowly and undergo less movement during embryogenesis (and hence are like plants, or “vegetal”).