MS-LS3 Genetics, heredity and variation
Aligned to MS-LS3 — Next Generation Science Standards.
What this lesson teaches
Genes are sections of DNA on chromosomes that carry instructions for traits, and offspring inherit a mix from both parents. Sexual reproduction and occasional mutations create variation, which is why siblings can look different even with the same parents. A Punnett square helps predict the chances of traits.
Worked example
If both parents carry one gene for brown eyes and one for blue, a Punnett square shows their child has a 3-in-4 chance of brown eyes and a 1-in-4 chance of blue. Each child gets a random combination, so siblings can end up with different eye colors.
Practice questions
- Where are the instructions for traits stored in a cell?
- Why can two siblings with the same parents look different?
- Use a Punnett square idea to find the chance of a recessive trait when both parents are carriers.
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
MS-LS3 Genética, herencia y variación
Los genes son secciones de ADN en los cromosomas que contienen instrucciones para los rasgos, y los descendientes heredan una combinación de ambos progenitores. La reproducción sexual y las mutaciones ocasionales crean variación, por eso los hermanos pueden verse distintos aunque tengan los mismos padres. El cuadro de Punnett ayuda a predecir las probabilidades de los rasgos.
Ejemplo: Si ambos progenitores tienen un gen para ojos cafés y uno para ojos azules, el cuadro de Punnett muestra que su hijo tiene 3 de 4 probabilidades de tener ojos cafés y 1 de 4 de tener ojos azules. Cada hijo recibe una combinación al azar, por lo que los hermanos pueden tener diferentes colores de ojos.
Teach this lesson today
An AI tutor that guides with questions instead of just giving answers — all K–12 core subjects, every child in the family.
Start free — no card required