Types of cleavage, Biology

Assignment Help:

Types of Cleavage

a) Radial Type: If each of the blastomeres of upper tier lies exactly over the corresponding blastomeres of the lower tier the pattern of cleavage is radially symmetrical i.e. blastomeres are arranged along the radii of the sphere, e.g. echinoderms, Amphioxus, amphibians.

b) Spiral Type: The upper tier of blastomeres of 8-cell stage embryo may be shifted with respect to the lower tier so that radially symmetrical arrangement of blastomeres is distorted in various degrees. In such a case the blastomeres of the upper tier do not lie exactly over the corresponding blastomeres of the lower tier.

Instead, all the blastomeres of upper tier are shifted in the same direction with respect to all the blastomeres of the lower tier. This position results from the oblique position of mitotic spindle so that, from the start, two daughter blastomeres do not lie one above the other, e.g., annelids, molluscs, some helminths of order polycladida.


Related Discussions:- Types of cleavage

Diminished oxygen-carrying capacity of hemoglobin, Manifestations of anemia...

Manifestations of anemia that are directly due to the diminished oxygen-carrying capacity of hemoglobin include: Answer A. pale skin. B. bleeding. C. bone pain. D. fatigue.

Embyonic development, What are the different patterns of cleavage (segmenta...

What are the different patterns of cleavage (segmentation of fertilized egg cell)?

Define about blood pressure control, Normal 0 false false f...

Normal 0 false false false EN-IN X-NONE X-NONE

What is intermittent treatment, Intermittent Treatment Intermittent 4...

Intermittent Treatment Intermittent 4-drug regimens with 2 or 3 doses per week after at least 2 weeks of daily therapy are also effective for treatment of TB and should alway

Explain the principle or theory of biuret method, Explain the Principle or ...

Explain the Principle or Theory of biuret method? If a strongly alkaline solution of Biuret is heated with very dilute copper sulphate, a violet colour is obtained. The substan

Define defensive proteins - biological functions of proteins, Define Defens...

Define Defensive Proteins - Biological Functions of Proteins? These proteins protect in opposition to diseases. Antibodies are the instance of defensive proteins. These combat

External sources for health care, Normal 0 false false fals...

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

Skin., what is the difference between fair skin and dark skin?

what is the difference between fair skin and dark skin?

Ringworm, R i n g w o r m It is also known as dermatophytosis re...

R i n g w o r m It is also known as dermatophytosis resulting in alopecia, scab formation and ring like lesions in the affected body parts. Eti o logy: Zeop

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd