Types of cleavage, Biology

TYPES OF CLEAVAGE -

Depending upon the distribution & amount of yolk, cleavage is of following types -

1.      HOLOBLASTIC EQUAL CLEAVAGE (holos, whole ; blastos, germs) -

In this type of cleavage the cleavage furrow take place in the whole egg.

It occurs in alecithal, mesolecithal & isolecithal eggs.

Forming blastomere are equal in size.

2.      HOLOBLASTIC UNEQUAL CLEAVAGE-

In this type of cleavage forming blastomeres are unequal. Small blastomeres are called micromeres.

Large blastomeres are called macromeres. It take place in the mesolecithal, telolecithal.

3.      MEROBLASTIC OR DISCOIDAL CLEAVAGE (Gr. meros, part)-

It take place in macrolecithal or heavily telolecithal egg. The cleavage take place only in the yolk free animal pole.

Mainly it take place the germinal disc or blasto disc. The yolk remains uncleaved.

4.      SUPERFICIAL CLEAVAGE -

This cleavage occur in centrolecithal eggs. It take place in the surface layer of the egg.

The central yolky part remains uncleaved. The peripheral ooplasm become multi nucleated.

On the basis of future of blatomeres, the cleavage is of 2 types -

1.       DETERMINATE CLEAVAGE -

It is also called as mosaic cleavage. In this cleavage a specific blastomere forms a specific part of the embryo.

Example - Tunicata, Cephalopoda, Nematoda.

2.       INDETERMINATE CLEAVAGE -

The fate of the blastomeres is not definite. If the two blastomeres after Ist cleavage get separated, both the cells form two different embryos. Similarly, if two fertilized eggs are fused, a single embryo is formed.

Example - Echinodermata, Hemichrodata & Vertebrates.

Note :-         The cleavage results in the formation of multicellular & solid ball-like morula.

The cleavage is controlled by protein synthesis which inturn is controlled by informosomes because during cleavage mRNA are not formed.

Posted Date: 10/3/2012 9:16:27 AM | Location : United States







Related Discussions:- Types of cleavage, Assignment Help, Ask Question on Types of cleavage, Get Answer, Expert's Help, Types of cleavage Discussions

Write discussion on Types of cleavage
Your posts are moderated
Related Questions
What are the three main steps for a good study of a genetic family tree? Step 1: to determine whether the studied phenotypical form has a dominant or recessive pattern. Step

Name two possible why the number of live bacteria cell have reached the stationary growth by 60hrs and start to die off after 12hrs?

Determine the Benedict's Test Glucose in urine is detected by Benedict's method and the test is known as Benedict's test. This test is used to detect glucose in urine (Glycosur

what are the 3 main excretory produces of mammals?

Explain the Probiotics in Foods? Yoghurts have been supplemented with probiotic strains of bifidobacteria and Lactobacilli. Milks fermented solely by intestinal isolates of lac

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

An egg osmometer Place some dilute hydrochloric acid or strong vinegar in a shallow dish, likeas a saucer, to a depth of about one centimetre. Hold the large end an egg in the

Mineral supplements There are two major classes of mineral sources: inorganic and organic. Organic complexes, however, have been shown to be more effectively absorbed by the a

Q. What is meant by the peripheral nervous system (PNS)? The peripheral nervous system comprehends the ganglia and nerves of the body.

Explain Classification of Protein based on amino acid content? Nutritionally, amino acids are classified on the basis of the body's ability to synthesize them - as essential (i