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Fertilization Restores Genetic Stability While Creating Diversity

Fertilization is the fusion of a sperm and an egg to form a zygote.
This process ensures the combination of genetic material from both parents, creating a new, genetically unique individual.

Note

The fusion of gametes restores the diploid chromosome number, which is halved during meiosis.

Fertilization Occurs in Four Key Steps

1. Sperm Navigation and Binding

Chemotaxis: Sperm are guided toward the egg by chemical signals.
Breaking Protective Layers:
1. Cumulus Oophorus: A cloud of follicle cells surrounding the egg.
2. Zona Pellucida: A glycoprotein layer that protects the egg.
3. Acrosome Reaction: Sperm release enzymes to digest the zona pellucida and reach the egg.

Tip

Without the acrosome reaction, sperm cannot penetrate the egg’s protective layers, preventing fertilization.

2. Fusion of Sperm and Egg Membranes

Proteins on the sperm bind to receptors on the egg membrane.
The membranes fuse, allowing the sperm nucleus to enter the egg.

Hint

Only the sperm nucleus enters the egg
The tail and mitochondria are left behind or destroyed.

3. Prevention of Polyspermy

Once a sperm enters, mechanisms ensure no additional sperm can fuse with the egg:
Cortical Reaction:
1. The egg releases enzymes that harden the zona pellucida, preventing further sperm entry.

Analogy

The cortical reaction acts like locking a door after one guest enters, ensuring no one else can get in.

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Note

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Tip

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Question 1

Recap question

If the cortical reaction in the egg fails to occur after a sperm enters, what is the most likely outcome?

Note

Fertilization is the process where a sperm cell and an egg cell combine to form a single cell called a zygote. This marks the beginning of a new human life.

The sperm and egg each carry half the genetic material needed for a human (23 chromosomes each).
When they combine, they restore the full set of 46 chromosomes.

DefinitionZygoteThe single cell formed when a sperm and egg fuse, containing a complete set of chromosomes.

AnalogyThink of fertilization like combining two halves of a puzzle - each half is unique, and together they form a complete picture.

Fertilization Restores Genetic Stability While Creating Diversity

Fertilization is the fusion of a sperm and an egg to form a zygote.
This process ensures the combination of genetic material from both parents, creating a new, genetically unique individual.

Note

The fusion of gametes restores the diploid chromosome number, which is halved during meiosis.

Fertilization Occurs in Four Key Steps

1. Sperm Navigation and Binding

Chemotaxis: Sperm are guided toward the egg by chemical signals.
Breaking Protective Layers:
1. Cumulus Oophorus: A cloud of follicle cells surrounding the egg.
2. Zona Pellucida: A glycoprotein layer that protects the egg.
3. Acrosome Reaction: Sperm release enzymes to digest the zona pellucida and reach the egg.

Tip

Without the acrosome reaction, sperm cannot penetrate the egg’s protective layers, preventing fertilization.

2. Fusion of Sperm and Egg Membranes

Proteins on the sperm bind to receptors on the egg membrane.
The membranes fuse, allowing the sperm nucleus to enter the egg.

Hint

Only the sperm nucleus enters the egg
The tail and mitochondria are left behind or destroyed.

3. Prevention of Polyspermy

Once a sperm enters, mechanisms ensure no additional sperm can fuse with the egg:
Cortical Reaction:
1. The egg releases enzymes that harden the zona pellucida, preventing further sperm entry.

Analogy

The cortical reaction acts like locking a door after one guest enters, ensuring no one else can get in.

Unlock the rest of this chapter with a Free account

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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Duis aute irure dolor in reprehenderit

Note

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Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

Questions

Recap questions

1 of 5

Question 1

Recap question

If the cortical reaction in the egg fails to occur after a sperm enters, what is the most likely outcome?

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Note

Fertilization is the process where a sperm cell and an egg cell combine to form a single cell called a zygote. This marks the beginning of a new human life.

The sperm and egg each carry half the genetic material needed for a human (23 chromosomes each).
When they combine, they restore the full set of 46 chromosomes.

DefinitionZygoteThe single cell formed when a sperm and egg fuse, containing a complete set of chromosomes.

AnalogyThink of fertilization like combining two halves of a puzzle - each half is unique, and together they form a complete picture.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

D3.1.6 Fertilization in humans Notes

Fertilization Restores Genetic Stability While Creating Diversity

Fertilization Occurs in Four Key Steps

1. Sperm Navigation and Binding

2. Fusion of Sperm and Egg Membranes

3. Prevention of Polyspermy

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Duis aute irure dolor in reprehenderit

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Fertilization Restores Genetic Stability While Creating Diversity

Fertilization Occurs in Four Key Steps

1. Sperm Navigation and Binding

2. Fusion of Sperm and Egg Membranes

3. Prevention of Polyspermy

Unlock the rest of this chapter with a Free account

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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