Sources of Genetic Variation
Aligned to HS-LS3-2 — Next Generation Science Standards.
What this lesson teaches
New inheritable variation arises in three ways: mutations change the DNA sequence, errors during copying alter it, and recombination shuffles the parents' genes into new combinations in the offspring.
Worked example
During meiosis, a mother's and a father's chromosomes swap matching segments, so a child inherits a mix neither parent had, one reason siblings differ despite sharing the same parents.
Practice questions
- List three sources of inheritable genetic variation.
- Show how crossing over during meiosis creates a new combination of genes.
- Defend a claim that mutation and recombination together explain the variety within a species.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Fuentes de variación genética
La nueva variación heredable surge de tres maneras: las mutaciones cambian la secuencia del ADN, los errores durante la copia la alteran y la recombinación mezcla los genes de los progenitores en nuevas combinaciones en la descendencia.
Ejemplo: Durante la meiosis, los cromosomas de la madre y del padre intercambian segmentos equivalentes, así que un hijo hereda una mezcla que ninguno de los progenitores tenía, una razón por la que los hermanos se diferencian aunque compartan los mismos padres.
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