Punnett Squares
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Science
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7th Grade
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Medium
+2
Standards-aligned
MATTHEW WILLIAMS
Used 9+ times
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42 Slides • 34 Questions
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Punnett Squares
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Punnett Squares
Graphical representation of possible genotypes of an offspring arising from two parents.
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Genotype
A two letter expression of a gene type.
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Mother's Genotype
The mother's genotype would be bb.
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Father's Genotype
The father's genotype would be Bb.
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Allele
Different versions of a gene that determine a specific trait.
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Each genotype is made of two alleles for the same gene.
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Every child inherits one allele for a specific trait from each parent.
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b = blue eyes
The mother has two b alleles for blue eyes. The mother has blue eyes.
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B = brown eyes
The father has one B allele for brown eyes and one b allele for blue eyes. B for brown is dominant over the recessive b for blue. The father has brown eyes.
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Dominant
The version of a gene allele that will manifest itself as a trait. Dominant alleles are written with capital letters. B dominant + b recessive = brown eyes.
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Recessive
The version of a gene allele that will only manifest itself when paired with the same allele. Recessive alleles are written with lower case letters.
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Recessive
The mother has two b-blue eye recessive alleles so she has blue eyes.
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Homozygous
Homo comes from the Greek word homos which means the same.
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Homozygous
Genes of the same allele; both dominant or both recessive.
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Homozygous
The mother has a homozygous genotype, bb. Both gene alleles are the same.
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Heterozygous
Hetero comes from the Greek word heteros which means other or different.
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Heterozygous
Genes of two different alleles; one dominant and one recessive.
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Heterozygous
The father has a heterozygous genotype, Bb. The gene alleles are different.
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Phenotype
The physical trait of a gene type.
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Phenotype
Phenotype is the actual physical trait.
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Phenotype
The mother's phenotype would be blue eyes.
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Phenotype
The father's phenotype would be brown eyes.
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Trait Probability in Offspring
The probability of an offspring being born with a certain trait is written as a ratio.
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Trait Probability in Offspring
There are four boxes in a Punnett Square. The possible ratios would be 0:4, 1:4, 2:4, 3:4, 4:4.
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Trait Probability in Offspring
The possible ratios would be read zero to four (0:4), one to four (1:4), two to four (2:4), three to four (3:4), four to four (4:4).
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SSSSSHHH!
Technically, 2:4 should be reduced like a fraction to 1:2 but I don't want to confuse the issue. We'll stick with 2:4. Don't tell Mrs. Russell or Mrs. Foster.
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Multiple Choice
What is the probability that these parents would have a child with brown eyes?
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Multiple Choice
What is the probability that these parents would have a child with blue eyes?
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Multiple Choice
What is the probability that these parents would have a child with green eyes?
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Curve Ball Time!
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How Would You Explain This?
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How Would You Explain This?
B = brown eyes / G and g = green eyes / b = blue eyes
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Multiple Choice
How would you explain this?
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Eye Color Dominance
Brown eyes are dominate over green and blue eyes. Green eyes are dominate over blue eyes.
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Multiple Choice
What is the probability that these parents would have a child with brown eyes?
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Multiple Choice
What is the probability that these parents would have a child with green eyes?
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Multiple Choice
What is the probability that these parents would have a child with blue eyes?
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Punnett Squares
Punnett Squares aren't just for humans and eye color.
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Punnett Squares
Punnett Squares can be used for any trait and any organism.
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Textbook
Turn to page 230 in the textbook.
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Multiple Choice
What is the purple flower allele?
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Multiple Choice
What is the white flower allele?
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Multiple Choice
Which trait is dominate, purple flowers or white flowers?
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Multiple Choice
Which trait is recessive, purple flowers or white flowers?
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Multiple Choice
What is the genotype for purple flowers?
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Multiple Choice
What is the genotype for white flowers?
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Multiple Choice
What is the probability that crossing purple flower pea plants with white flower pea plants will produce pea plants with purple flowers?
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Multiple Choice
What is the probability that crossing purple flower pea plants with white flower pea plants will produce pea plants with white flowers?
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Multiple Choice
Look at page 231: What is the round pea allele?
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Multiple Choice
What is the wrinkled pea allele?
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Multiple Choice
What is the genotype for both parent peas? (look at the top and side of the Punnett Square)
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Rr
Write Rr in your textbook next to genotype under both peas.
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Multiple Choice
Since the round pea allele (R) is dominate, what would the phenotype for both parent peas be?
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Round Pea
Write round pea next to phenotype beneath both pea pictures.
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Now Fill In The Punnett Square
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Multiple Choice
What genotype would go in the top left box?
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RR
Write RR in the top left box. Write RR next to genotype. Write round pea next to phenotype.
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Multiple Choice
What genotype would go in the top right and bottom left boxes?
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Rr
Write Rr in the top right and bottom left boxes. Write Rr next to genotype in the top right and bottom left boxes. Write round pea next to phenotype in the top right and bottom left boxes.
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Multiple Choice
What genotype would go in the bottom right box?
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rr
Write rr in the bottom right box. Write rr next to genotype in the bottom right box. Write wrinkled pea next to phenotype in the bottom right box.
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Multiple Choice
What is the probability that the two parent pea plants will produce pea plants with round peas?
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Multiple Choice
What is the probability that the two parent pea plants will produce pea plants with wrinkled peas?
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Page 233
The dominate B allele is for guinea pigs with black fur and the recessive b allele is for guinea pigs with brown fur.
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Multiple Choice
How many homozygous genotypes are in the guinea pig Punnett Square?
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Multiple Choice
How many heterozygous genotypes are in the guinea pig Punnett Square?
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Multiple Choice
Different versions of a gene that determine a specific trait.
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Multiple Choice
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Multiple Choice
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Multiple Choice
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Multiple Choice
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Multiple Choice
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Multiple Choice
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Multiple Choice
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Put Your Textbook Up
Punnett Squares
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