#Question id: 5660
#Unit 5. Developmental Biology
Following statement regarding to acrosome reaction in sea urchin.
A. Activation of the acrosome reaction serves as a barrier to intraspecies fertilizations.
B. The acrosome reaction is initiated by sulfate-containing polysaccharides in the egg jelly that bind to specific receptors located directly above the acrosomal vesicle on the sperm cell membrane.
C. These polysaccharides are often highly species specific, but egg jelly factors from one species of sea urchin generally activate the acrosome reaction in closely related species.
D. The elevated Ca2+ level in a relatively basic cytoplasm triggers the fusion of the acrosomal membrane with the adjacent sperm cell membrane, releasing enzymes that can lyse a path through the egg jelly to the vitelline envelope.
Which of the following statements are correct?
#Question id: 5661
#Unit 5. Developmental Biology
Following statements regarding to the embryogenesis in A. thaliana.
A. The first zygotic division is unequal, with the basal cell larger than the apical cell. The basal cell divides to give rise to the suspensor. The apical cell divides vertically to form a two-celled proembryo, which will give rise to the rest of the embryo.
B. The top most suspensor cell is recruited into the embryo, where it is known as the hypophysis, and contributes to the embryonic root meristem and root cap.
C. The next two divisions produce an eight-cell octant-stage embryo, which develops into a heart-stage embryo of around 32 cells
D. The embryo elongates and the cotyledons start to develop as wing-like structures at one end, while an embryonic root forms at the other. This stage is known as the globular stage.
Which of the following statements are correct?
#Question id: 5662
#Unit 5. Developmental Biology
Mouse sperm contain receptor proteins that bind to a glycoprotein (ZP3) in the zona pellucida of mouse eggs. Binding of ZP3 receptors to ZP3 initiates the sperm’s acrosomal reaction. All of the following experimental observations would be expected EXCEPT:
#Question id: 5663
#Unit 5. Developmental Biology
Following statements are related to slow block to polyspermy in mammals.
A. A First slow block to polyspermy comes When the cortical granules fuse with the egg cell membrane, they release protein-digesting enzymes which is called as ovastacin that modify the zona pellucida proteins.
B. A second slow block to polyspermy comes from the so-called zinc spark, the release of billions of zinc ions that is induced by the entry of the first sperm, these released zinc ions are seen to bind to the egg cell membrane form a “zinc shield” that prevents further sperm entry.
C. A third slow block to polyspermy occurs at the level of the egg cell membrane and involves Juno.
Which of the following is incorrect?
#Question id: 5664
#Unit 5. Developmental Biology
Following statements are regarding to gamete fusion and the prevention of polyspermy in mammals.
A. In mammals, it is not the tip of the sperm head that makes contact with the egg but the side of the sperm head.
B. The junction between the inner acrosomal membrane and the sperm cell membrane is called the acrosomal region, and this is where membrane fusion between sperm and egg begins.
C. Sperm-egg fusion appears to involve several proteins, two of which are Izumo, in the oocyte membrane, and Juno, in the acrosomal membrane.
D. These fusion proteins bind together and appear to recruit other proteins to make an adhesion and fusion complex.
Which of the following statements are correct?
#Question id: 5665
#Unit 5. Developmental Biology
Following statements are regarding to cortical granule reaction.
A. To initiating the slow block to polyspermy the release of Ca2+ that occurs when the sperm enters the egg is critical for activating the egg’s metabolism and initiating development
B. Calcium ions release the inhibitors from maternally stored messages, allowing these mRNAs to be translated
C. Calcium ions are not release the inhibition of nuclear division, thereby allowing cleavage to occur.
D. Udx1, the enzyme responsible for the reduction of oxygen to crosslink the fertilization envelope, is also NADPH-dependent
E. The fertilization envelope is elevated from the cell membrane by glycosaminoglycans which provides support for the blastomeres during cleavage
Which of the following combinations are correct?