Flashcards · Biology · Inheritance
Single Gene Inheritance and Punnett Squares
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What does a Punnett square show?
The possible combinations of gametes in a cross.
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What are the gametes of a Tt parent?
T and t.
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What are the offspring of Tt x Tt?
1 TT : 2 Tt : 1 tt.
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What is the phenotype ratio of Tt x Tt?
3 dominant : 1 recessive.
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What is the probability of tt in Tt x Tt?
1 in 4, or 25%.
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What are the offspring of TT x tt?
All Tt.
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What are the offspring of Tt x tt?
1 Tt : 1 tt.
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What is a carrier?
A person with a recessive allele who does not show the disorder.
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What are the sex chromosomes of a female?
XX.
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What are the sex chromosomes of a male?
XY.
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What does every egg carry?
An X chromosome.
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What do sperm carry?
Half an X, and half a Y.
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What is the probability of a boy?
50%, or 1 in 2.
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Why might the results of a cross not match the ratio?
Fertilisation is random, so small numbers can vary.
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Are most features controlled by a single gene?
No, by many genes.
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Common mistake about genetic diagrams?
Not showing the gametes. Always write them before filling in the grid.