Cleavage - Basic

Cleavage - Basic

Dear Readers,

Cleavage is the division of cells in the early embryo. The process follows fertilisation, with the transfer being triggered by the activation of a cyclin-dependent kinase complex.The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula.

Q1. Unit cell of blastula is

•  Micromere
•  Megamere
•  Blastomere
•  None of the above

Blastomere

Q2. In an egg, the type of cleavage is determined by the

•  Shape and size of the sperm
•  Size and location of the nucleus
•  Amount and distribution of yolk
•  Number of egg membranes

Amount and distribution of yolk

Q3. How many cleavages occur for the formation of 32 cells

•  3
•  4
•  5
•  6

5

Q4. The cleavage having incomplete division of egg is known as

•  Holoblastic
•  Meroblastic
•  Meridional
•  Spiral

Meroblastic

Q5. Blastula lacks

•  Blastomeres
•  Blastoderm
•  Blastocoel
•  Blastopore

Blastopore

Q6. In spiral cleavage turn of spiral may be

•  Clockwise
•  Anticlockwise
•  Both (a) and (b)
•  None of the above

Both (a) and (b)

Q7. Blastocyst is a modified blastula of

•  Placental mammals
•  Frog
•  Fish
•  Birds

Placental mammals

Q8. Cleavage in bird’s egg is

•  Equal and holoblastic
•  Unequal and holoblastic
•  Discoidal meroblastic
•  Superficial meroblastic

Discoidal meroblastic

Q9. The blastula of prototherians is called

•  Blastocyst
•  Stereoblastula
•  Coeloblastula
•  Discoblastula

Discoblastula

Q10. In frog equal holoblastic cleavage does not found due to

•  A dark pigment in animal pole
•  Heavy yolk in vegetal pole
•  Yolk concentrated in center of egg
•  Nucleus is assymetrical in position

Heavy yolk in vegetal pole