IB Biology Topic D3.2.12 Haemophilia as an Example of a Sex-linked Genetic Disorder Revision Notes (SL/HL)

IB Biology Topic D3.2.12 Haemophilia as an Example of a Sex-linked Genetic Disorder Revision Notes (SL/HL) | RevisionDojo

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Haemophilia Stops Blood from Clotting Properly

In haemophilia, a small cut can keep bleeding because the blood cannot clot properly.
The body cannot make enough Factor VIII (haemophilia A) or Factor IX (haemophilia B), both of which are needed for clotting.

Definition

Haemophilia

Haemophilia is a disorder where blood fails to clot properly due to a deficiency in a clotting factor.

The Faulty Gene Is Carried on the X Chromosome

The Factor VIII gene sits on the X chromosome, which makes haemophilia an X-linked recessive disorder.
1. Males ($X^hY$) are affected if their single X carries the faulty allele.
2. Females are affected only if both X chromosomes carry it, so they are usually carriers instead.

Hint

A carrier's healthy X allele makes enough Factor VIII, so she stays unaffected.
She can still pass the faulty allele to her children.

Why Males Are Affected More Often

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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.

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Haemophilia Stops Blood from Clotting Properly

In haemophilia, a small cut can keep bleeding because the blood cannot clot properly.
The body cannot make enough Factor VIII (haemophilia A) or Factor IX (haemophilia B), both of which are needed for clotting.

Definition

Haemophilia

Haemophilia is a disorder where blood fails to clot properly due to a deficiency in a clotting factor.

The Faulty Gene Is Carried on the X Chromosome

The Factor VIII gene sits on the X chromosome, which makes haemophilia an X-linked recessive disorder.
1. Males ($X^hY$) are affected if their single X carries the faulty allele.
2. Females are affected only if both X chromosomes carry it, so they are usually carriers instead.

Hint

A carrier's healthy X allele makes enough Factor VIII, so she stays unaffected.
She can still pass the faulty allele to her children.

Why Males Are Affected More Often

Definition

Paywall

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

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

Note

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.

Excepteur sint occaecat cupidatat non proident

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.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic D3.2.12: Haemophilia as an Example of a Sex-linked Genetic Disorder Notes

Haemophilia Stops Blood from Clotting Properly

The Faulty Gene Is Carried on the X Chromosome

Why Males Are Affected More Often

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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Haemophilia Stops Blood from Clotting Properly

The Faulty Gene Is Carried on the X Chromosome

Why Males Are Affected More Often

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

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics