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

Define precaution for estimation of vitamin c in lemon juice, Define precau...

Define precaution for estimation of vitamin c in lemon juice? 1. Rinse all glassware with 3% metaphosphoric acid before you begin your practical and subsequently each time you

Adenine and thymine in complementary strands dna molecule, A "phosphodieste...

A "phosphodiester bond" links together: Answer the 3' hydroxyl group and the N9 atom of adenine in ATP. The Phosphate group and N9 atom of adenine in ATP. Sequential nucleosides in

What is catalyzes a substrate level phosphorylation, The enzyme in the TCA ...

The enzyme in the TCA cycle that catalyzes a substrate level phosphorylation is -citrate dehydrogenase -succinate thiokinase -isocitrate dehydrogenase

Determine the significance of lingual nerve and artery, Significance of Lin...

Significance of Lingual nerve and artery Because the nerve lies medial to the retromolar pad, incisions in this region should remain lateral to the pad and mucosal reflection s

State the versions of binocular movements, State the Versions of Binocular ...

State the Versions of Binocular movements Versions are movements of both eyes in the same direction. a) Dextroversions: Movements of both eyes to'the right side. b) Levov

Parasitology, how trematodes/nematodes adapt to their parasitic mode of fee...

how trematodes/nematodes adapt to their parasitic mode of feeding

Explain the procedure of taking blood pressure, Explain the Procedure of Ta...

Explain the Procedure of Taking Blood Pressure - Explain the procedure to the patient. In case patient is coming for first time to check the blood pressure explain to the patie

How do malign neoplasias appear, Q. How do malign neoplasias appear? Th...

Q. How do malign neoplasias appear? The Neoplasias appear due to DNA mutations in genes that regulate the cellular proliferation thus making the cell lose its capacity to contr

What is the role of linked traits in genetics, What is the role of Linked T...

What is the role of Linked Traits in genetics? In his study of inheritance in the fruit fly, Morgan observed that certain genes are distributed together, or linked, rather than

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