Biology · GCSE · Reproduction & Genetics

Sex determination

Sex determinationFree4:24Heddy Score 3 of 7, below the standard

What you need to know

  • Human body cells have 23 pairs of chromosomes, and one pair is the sex chromosomes.
  • XX usually develops as female and XY as male.
  • An egg carries an X chromosome, while a sperm carries either an X or a Y.
  • A Punnett square of that cross gives an equal chance of female and male offspring.
  • Individual families do not always match that equal chance.

In this clip

Runs 4:24, from 0:00 to 4:24 of the full video.

Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

532K views · 3.22K likes · FuseSchool - Global Education 933K subscribers

As reported by YouTube on 2026-11-02. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

It builds the XX and XY cross properly, from gametes to the expected ratio.

FuseSchool - Global Education on YouTubechecked 2026-10-18

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