Development of Xenopus laevis, Part 2
Fertilization
When a seeking out a mate, a male Xenopus will emit a mating call under
the water which is hardly able to be detected in the air. The female
will respond, joining the male in a duet if she is responsive, or will
reject him with a clicking sound. Upon finding a receptive female, the
male, who is much smaller, will climb on to his mate’s back. Th
e two express their gametes simultaneously, resulting in completely external fertilization.
Xenopus eggs are two-toned, with the darker half, known as the animal
hemisphere, on top to protect the DNA in the egg from UV radiation. The
lighter colored, denser half on bottom, known as the vegetal hemisphere,
contains the yolk that will nourish the forming embryo.
The
sperm enters the animal hemisphere, as the vegetal side is far too
dense. When the sperm fuses with the oolemma (the plasma membrane of the
oocyte), it depolarizes, which serves a fast block to other sperm
trying to fertilize the egg (polyspermy). A slow block to polyspermy
comes in the formation of the fertilization envelope, via cortical
granule exocytosis.
About 1-2 hours past fertilization, the
cortex rotates approximately 30 degrees so that the center of the animal
hemisphere (known as the animal pole) aligns with the sperm entry
point. As this rotation occurs, previously pigmented areas of cortical
cytoplasm are exposed. This is known as the grey crescent, and is the
first step in dorsoventral patterning. This area will give rise to the
dorsal side.
For more information: http://
Photo credit: http://www.xenopus.com/
Development of Xenopus laevis, Part 2
Fertilization
When a seeking out a mate, a male Xenopus will emit a mating call under the water which is hardly able to be detected in the air. The female will respond, joining the male in a duet if she is responsive, or will reject him with a clicking sound. Upon finding a receptive female, the male, who is much smaller, will climb on to his mate’s back. Th
Fertilization
When a seeking out a mate, a male Xenopus will emit a mating call under the water which is hardly able to be detected in the air. The female will respond, joining the male in a duet if she is responsive, or will reject him with a clicking sound. Upon finding a receptive female, the male, who is much smaller, will climb on to his mate’s back. Th
e two express their gametes simultaneously, resulting in completely external fertilization.
Xenopus eggs are two-toned, with the darker half, known as the animal hemisphere, on top to protect the DNA in the egg from UV radiation. The lighter colored, denser half on bottom, known as the vegetal hemisphere, contains the yolk that will nourish the forming embryo.
The sperm enters the animal hemisphere, as the vegetal side is far too dense. When the sperm fuses with the oolemma (the plasma membrane of the oocyte), it depolarizes, which serves a fast block to other sperm trying to fertilize the egg (polyspermy). A slow block to polyspermy comes in the formation of the fertilization envelope, via cortical granule exocytosis.
About 1-2 hours past fertilization, the cortex rotates approximately 30 degrees so that the center of the animal hemisphere (known as the animal pole) aligns with the sperm entry point. As this rotation occurs, previously pigmented areas of cortical cytoplasm are exposed. This is known as the grey crescent, and is the first step in dorsoventral patterning. This area will give rise to the dorsal side.
For more information: http://
Photo credit: http://www.xenopus.com/
Xenopus eggs are two-toned, with the darker half, known as the animal hemisphere, on top to protect the DNA in the egg from UV radiation. The lighter colored, denser half on bottom, known as the vegetal hemisphere, contains the yolk that will nourish the forming embryo.
The sperm enters the animal hemisphere, as the vegetal side is far too dense. When the sperm fuses with the oolemma (the plasma membrane of the oocyte), it depolarizes, which serves a fast block to other sperm trying to fertilize the egg (polyspermy). A slow block to polyspermy comes in the formation of the fertilization envelope, via cortical granule exocytosis.
About 1-2 hours past fertilization, the cortex rotates approximately 30 degrees so that the center of the animal hemisphere (known as the animal pole) aligns with the sperm entry point. As this rotation occurs, previously pigmented areas of cortical cytoplasm are exposed. This is known as the grey crescent, and is the first step in dorsoventral patterning. This area will give rise to the dorsal side.
For more information: http://
Photo credit: http://www.xenopus.com/
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