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Questions and Answers
In a cross between two homozygous black furred animals ($BB$), what is the probability of their offspring having white fur?
In a cross between two homozygous black furred animals ($BB$), what is the probability of their offspring having white fur?
- 25%
- 100%
- 0% (correct)
- 75%
If a homozygous black furred animal ($BB$) is crossed with a homozygous white furred animal ($bb$), what is the genotype of the F1 generation?
If a homozygous black furred animal ($BB$) is crossed with a homozygous white furred animal ($bb$), what is the genotype of the F1 generation?
- A mix of $BB$ and $bb$
- $bb$
- $BB$
- $Bb$ (correct)
In a monohybrid cross between a black furred animal ($Bb$) and a white furred animal ($bb$), what percentage of the offspring would you expect to have the white fur phenotype?
In a monohybrid cross between a black furred animal ($Bb$) and a white furred animal ($bb$), what percentage of the offspring would you expect to have the white fur phenotype?
- 0%
- 75%
- 50% (correct)
- 25%
What is the probability of a homozygous dominant individual ($BB$) producing a gamete carrying the dominant allele ($B$)?
What is the probability of a homozygous dominant individual ($BB$) producing a gamete carrying the dominant allele ($B$)?
Which of the following statements about the F1 generation resulting from a cross between two homozygous parents with different phenotypes is always true when alleles interact with each other by complete dominance?
Which of the following statements about the F1 generation resulting from a cross between two homozygous parents with different phenotypes is always true when alleles interact with each other by complete dominance?
What is the expected phenotypic ratio in the F2 generation resulting from a cross between two heterozygous individuals ($Bb$ x $Bb$)?
What is the expected phenotypic ratio in the F2 generation resulting from a cross between two heterozygous individuals ($Bb$ x $Bb$)?
In a cross between two heterozygous black furred animals ($Bb$), what is the probability of producing a white furred offspring ($bb$)?
In a cross between two heterozygous black furred animals ($Bb$), what is the probability of producing a white furred offspring ($bb$)?
Which of the following genotypes would NOT be found in the F2 generation of a monohybrid cross starting with homozygous parents ($BB$ and $bb$)?
Which of the following genotypes would NOT be found in the F2 generation of a monohybrid cross starting with homozygous parents ($BB$ and $bb$)?
If you cross two F1 generation individuals ($Bb$), what is the probability that the offspring will be heterozygous ($Bb$)?
If you cross two F1 generation individuals ($Bb$), what is the probability that the offspring will be heterozygous ($Bb$)?
What term describes the offspring resulting from a cross between two members of the F1 generation?
What term describes the offspring resulting from a cross between two members of the F1 generation?
Which of the following crosses will result in offspring that are all heterozygous?
Which of the following crosses will result in offspring that are all heterozygous?
A farmer crosses two plants. One has purple flowers (dominant, $P$) and the other has white flowers (recessive, $p$). All of the resulting offspring have purple flowers. What are the most probable genotypes of the parent plants?
A farmer crosses two plants. One has purple flowers (dominant, $P$) and the other has white flowers (recessive, $p$). All of the resulting offspring have purple flowers. What are the most probable genotypes of the parent plants?
If a genetic cross yields a 3:1 phenotypic ratio in the offspring, what does this typically suggest about the genotypes of the parents?
If a genetic cross yields a 3:1 phenotypic ratio in the offspring, what does this typically suggest about the genotypes of the parents?
Which of the following statements best describes the relationship between probability and actual outcomes in genetics?
Which of the following statements best describes the relationship between probability and actual outcomes in genetics?
A plant breeder crosses two pea plants and observes that approximately 75% of the offspring have purple flowers and 25% have white flowers. Based on this observation, what can the breeder conclude about the genotypes of the parent plants, assuming purple flowers are dominant (P) and white flowers are recessive (p)?
A plant breeder crosses two pea plants and observes that approximately 75% of the offspring have purple flowers and 25% have white flowers. Based on this observation, what can the breeder conclude about the genotypes of the parent plants, assuming purple flowers are dominant (P) and white flowers are recessive (p)?
Flashcards
Homozygous
Homozygous
Having two identical alleles for a gene (e.g., BB or bb).
Phenotype
Phenotype
The physical expression of a gene (e.g., black fur).
Genotype
Genotype
The genetic makeup of an organism (e.g., BB, Bb, bb).
Gamete
Gamete
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Punnett Square
Punnett Square
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Dominant Allele
Dominant Allele
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Recessive Allele
Recessive Allele
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F1 Generation
F1 Generation
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Heterozygous
Heterozygous
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F2 Generation
F2 Generation
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Heterozygous Cross
Heterozygous Cross
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Pure-Breeding
Pure-Breeding
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Phenotypic Ratio
Phenotypic Ratio
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Probability
Probability
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Capital Letter Allele
Capital Letter Allele
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Study Notes
- A Punnett square predicts offspring genotypes and phenotypes from a cross.
- Types of gametes from one parent are on the Punnett square's right side; those from the other parent are at the top.
- Offspring genotypes and phenotypes appear in the Punnett square's boxes.
- Homozygous parents (BB) produce offspring (BB) with the same genotype and phenotype (black fur).
- Crosses between the homozygous individuals result in offspring with a BB genotype and black fur phenotype.
- An event certain to occur has a probability of 1; one certain to never occur has a probability of 0.
- The probability of black fur offspring from the cross is 1 and the probability of white fur is 0.
- Pure-breeding refers to breeding homozygous individuals with identical alleles for a gene.
- Pure-breeding leads to offspring with the same homozygous genotype as their parents.
F1 Generation
- The first filial generation (F1) is from crossing two homozygous individuals with different phenotypes.
- For example, crossing a homozygous dominant black fur parent (BB) with a homozygous recessive white fur parent (bb).
- The black fur allele (B) is dominant and the white fur allele (b) is recessive.
- Gametes from the BB parent carry the B allele; gametes from the bb parent carry the b allele.
- The probability of the BB parent producing a gamete with the B allele is 1, and the probability of the bb parent producing a gamete with the b allele is 1.
- All offspring (F1 generation) have a Bb genotype and black fur phenotype.
- F1 generation members are heterozygous.
- Members of the F1 generation express the dominant phenotype when alleles interact with complete dominance.
Crosses Between Heterozygous Individuals
- The second filial generation (F2 generation) comes from crossing two members of the F1 generation.
- Each heterozygous parent produces two gamete types: B and b.
- The probability of a parent producing a gamete with the B allele is 1/2 (0.5), and the probability of a gamete with the b allele is also 1/2 (0.5).
- The Punnett square shows Bb genotype appears in two of four boxes, BB in one box, and bb in one box.
- The probability of a Bb offspring is 2/4 (0.5), BB is 1/4 (0.25), and bb is 1/4 (0.25).
- The overall probability of black fur offspring is 3/4 (0.75), and white fur is 1/4 (0.25).
- The phenotypic ratio of black to white fur is 3:1.
- Heterozygous individuals with the same phenotype may not produce offspring that look like them.
- Breeding between heterozygous individuals is not considered pure-breeding.
Probability in Genetics
- With a 3 in 4 chance of black fur offspring there is no guarantee that 3 out of 4 offspring will have black fur.
- The actual outcome and event probability are not always the same, unless the probability is 0 or 1.
- A coin toss has a 1 in 2 chance of heads and a 1 in 2 chance of tails, though four tosses may not yield two heads and two tails.
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Description
Explore Punnett squares for predicting offspring genotypes and phenotypes. Understand how parental gametes determine offspring traits within the square. Learn about homozygous crosses, probability in genetics, and pure-breeding.
