Lecture 23

Lecture 23 - Lecture 23 Objectives Chapter 7: Amphibians...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 23 Objectives Chapter 7: Amphibians and Fish 1. Describe the restructuring of microtubules following fertilization and the role of the oriented microtubules in the specification of the anterior-posterior and dorsal-ventral axes. - In fertilization the point of sperm entry is important because it determines the orientation of the dorsal-ventral axis and anterior posterior of the larva (tadpole). The point of sperm entry will mark the ventral point of the embryo, while the site 180 o opposite of that point will mark the dorsal side. The sperm centriole organizes the microtubules of the egg and causes them to arrange in a parallel array in the vegetal cytoplasm, separating the cotical cytoplasm from the yolky internal cytoplasm. The arrays are first seen immediately before rotation starts, and then disappear when rotation ceases. (Fig 7-1) 2. Describe cleavage and gastrulation in frogs. - Cleavage is radially symmetric and holoblastic, just like echinoderm cleavage. The amphibian egg, however, contains much more yolk which is concentrated in the vegetal hemisphere and is an impediment to cleavage. The first division begins at the animal pole and slowly extends down into the vegetal region and bisects the gray crescent. At this point one can see the difference in the furrows
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/10/2010 for the course BIOS 7676 taught by Professor Sanders during the Spring '10 term at LA Tech.

Page1 / 2

Lecture 23 - Lecture 23 Objectives Chapter 7: Amphibians...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online