A still of the Breeding planner this video shows. The screen reads: Why only 1 in 4?.
Why one pup in four? The Punnett square
Your channel hereExplainer · 60 seconds
Explain why two heterozygous parents give one homozygous pup in four, with the Punnett square from the breeding planner.
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What to do and say
A sample script of about 110 words. Say it your own way.
- 0:00
DoOpen on the Punnett square from a fl/+ by fl/+ plan, and ask why only one box is fl/fl.
SayTwo heterozygous parents. Why is only one pup in four homozygous?
- 0:05
DoExplain that each parent passes on one of its two copies at random.
SayEach parent has two copies of the gene, one floxed and one wild type. It passes on one of them at random, so each copy has a half chance.
- 0:20
DoPoint to the boxes: fl/fl in one of four, fl/+ in two, +/+ in one.
SayA pup is homozygous only if both parents pass on the floxed copy. A half times a half is a quarter. Two boxes are heterozygous, and one is wild type.
- 0:35
DoShow the table under the square, which splits each share between males and females.
SayThe table under the square splits each share between males and females, so you can plan for the sex you need too.
- 0:50
DoSay why labs plan extra litters, and where the planner is.
SayA quarter is an average, and some litters get fewer, so labs plan extra. Plan yours free at conductcolony.com.
Posting it yourself? Say that ConductScience paid you, in the video or the caption, and use the platform's paid partnership label if it has one.
What viewers should learn
Each parent passes on one of its two copies at random, so two heterozygous parents give a homozygous pup one time in four, on average.
Classic study: Mendel, 1866.
Try it before you film
Open it first: Breeding planner on conductcolony.com. It needs no account. It runs in your browser, and nothing you enter is sent or stored.
Use sample animals and IDs you make up, not a real colony. Never show real participants, children, patients, private records or unpublished results. Get permission before you film at your school or workplace, or name it. The handbook has the rest.