wunder beta🌱 Predicting Inherited Traits
Dominant, recessive, and the four-box Punnett square, learn Mendel's rules of heredity and predict a Bb x Bb cross's famous 3 to 1 ratio.
What you’ll learn
- The Rules of InheritanceDefine genes and alleles, distinguish dominant from recessive, and explain genotype versus phenotype.Traits pass to offspring through genes, with each individual carrying two alleles per gene, one from each parent, a rule Gregor Mendel discovered with pea plants. A dominant allele (capital letter) shows even in one copy, while a recessive allele (lowercase) shows only with two. Genotype is the allele pair; phenotype is the visible trait.
- The Punnett SquareBuild a Punnett square for a Bb x Bb cross, and use it to predict the 3 to 1 ratio of dominant to recessive offspring.A Punnett square lays parent alleles along a grid and fills each box to show every possible offspring genotype. A Bb x Bb cross gives BB, Bb, Bb, and bb, a 3 to 1 ratio of dominant to recessive traits. Mendel saw this same 3 to 1 ratio in his yellow and green peas, confirming the prediction.
Questions this course answers
Whose pea plant experiments revealed the rules of inheritance?
Gregor Mendel discovered the rules of heredity by breeding and counting thousands of pea plants in the 1860s.
What is the difference between a dominant and a recessive allele?
A dominant allele shows up whenever it is present, while a recessive allele only shows when two copies are inherited.
Which genotype will show the recessive trait?
Only bb, two recessive alleles with no dominant one, shows the recessive trait.
In a Bb x Bb cross, what are the four possible offspring genotypes?
Combining Bb and Bb in a Punnett square gives BB, Bb, Bb, and bb.
What ratio of dominant to recessive traits does a Bb x Bb cross predict?
Three of the four boxes (BB, Bb, Bb) show the dominant trait and one (bb) shows the recessive, a 3 to 1 ratio.
Mendel crossed peas that were Yy (yellow) with each other. Roughly what share of offspring had green (yy) seeds?
A Yy x Yy cross gives a 3 to 1 ratio, so about one-quarter of the offspring are yy and show green seeds.
Grounded in trusted sources
- Britannica
- National Geographic
- Understanding Evolution (UC Berkeley)
- Smithsonian
Every Wunder lesson is built from real, reputable sources — never invented.
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