IB Biology Topic D2.1.11 Meiosis as a Source of Variation Revision Notes (SL/HL)

IB Biology Topic D2.1.11 Meiosis as a Source of Variation Revision Notes (SL/HL) | RevisionDojo

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Crossing Over: Homologous Chromosomes Swap Alleles in Prophase I

During prophase I, each pair of homologous chromosomes lines up together to form a bivalent.
Non-sister chromatids, the chromatids belonging to the two different homologues, then exchange matching segments of DNA.
This exchange happens at cross-over points called chiasmata (singular: chiasma).
Crossing over is random and can occur at many points along a chromosome.
The result is recombinant chromosomes that carry a new mix of maternal and paternal alleles.

Common Mistake

Crossing over swaps alleles, not whole chromosomes.
It happens between non-sister chromatids of homologous chromosomes, never between sister chromatids.

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Crossing Over: Homologous Chromosomes Swap Alleles in Prophase I

During prophase I, each pair of homologous chromosomes lines up together to form a bivalent.
Non-sister chromatids, the chromatids belonging to the two different homologues, then exchange matching segments of DNA.
This exchange happens at cross-over points called chiasmata (singular: chiasma).
Crossing over is random and can occur at many points along a chromosome.
The result is recombinant chromosomes that carry a new mix of maternal and paternal alleles.

Common Mistake

Crossing over swaps alleles, not whole chromosomes.
It happens between non-sister chromatids of homologous chromosomes, never between sister chromatids.

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 D2.1.11: Meiosis as a Source of Variation Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Crossing Over: Homologous Chromosomes Swap Alleles in Prophase I

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Crossing Over: Homologous Chromosomes Swap Alleles in Prophase I

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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