Meiosis: Sources of Genetic Variation Simplified Revision Notes for A-Level AQA Biology

Revision notes with simplified explanations to understand Meiosis: Sources of Genetic Variation quickly and effectively.

Learn about Genetic Diversity: Mutations & Meiosis for your A-Level Biology Exam. This Revision Note includes a summary of Genetic Diversity: Mutations & Meiosis for easy recall in your Biology exam

264+ students studying

4.3.5 Meiosis: Sources of Genetic Variation

infoNote

Meiosis produces genetically different cells through two key processes that introduce variation: independent assortment of chromosomes and crossing over of chromatids. These mechanisms ensure that offspring inherit unique combinations of genetic material.

Sources of Genetic Variation

Independent Assortment of Chromosomes

During meiosis I, homologous chromosomes line up in pairs along the equator of the cell.
The orientation of each pair is random, meaning that the maternal or paternal chromosome can go to either daughter cell.
This creates different combinations of chromosomes in the gametes.
For example, in humans with 23 pairs of chromosomes, there are 2²³ (over 8 million) possible combinations of chromosomes from independent assortment alone.

Crossing Over of Chromatids

Crossing over occurs during prophase I of meiosis when homologous chromosomes form pairs called bivalents.
The chromatids of homologous chromosomes intertwine and sections of DNA are exchanged between them at points called chiasmata.
This leads to a new combination of alleles on each chromosome, increasing genetic diversity.
For example, a chromosome may now carry alleles from both the maternal and paternal chromosomes.

infoNote

Summary

Independent assortment results in random combinations of whole chromosomes in gametes.
Crossing over creates recombinant chromosomes with unique combinations of alleles.
These processes ensure that each gamete is genetically unique, contributing to variation in offspring when gametes fuse during fertilisation.

infoNote

Key Exam Tips

Use diagrams to illustrate independent assortment and crossing over in meiosis I.
Remember: crossing over happens during prophase I, and independent assortment occurs during metaphase I.
Understand how these mechanisms contribute to evolution by increasing genetic variation in populations.

500K+ Students Use These Powerful Tools to Master Meiosis: Sources of Genetic Variation For their A-Level Exams.

Enhance your understanding with flashcards, quizzes, and exams—designed to help you grasp key concepts, reinforce learning, and master any topic with confidence!

70 flashcards

Flashcards on Meiosis: Sources of Genetic Variation

Revise key concepts with interactive flashcards.

Try Biology Flashcards

7 quizzes

Quizzes on Meiosis: Sources of Genetic Variation

Test your knowledge with fun and engaging quizzes.

Try Biology Quizzes

5 questions

Exam questions on Meiosis: Sources of Genetic Variation

Boost your confidence with real exam questions.

Try Biology Questions