Questions and Answers
If a plant with purple, axial flowers and green, inflated pods is heterozygous for all four genes, how many different types of gametes can it produce?
16
Which individual could produce the four possible gametes: SRb, Sri, sRb, and srb?
SsRrbb
What are the genotypes of the parents that produce four offspring with varying fur types from a male with short, black fur and a female with long, white fur?
llBb x Llbb
What is the gamete produced by an individual with genotype SSRRbb?
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What gametes can be produced by an individual with the genotype ssRrBB?
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What gametes can be produced by an individual with the genotype SsRrbb?
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What gametes can be produced by an individual with the genotype SsRrBb?
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Based on Mendel's law of independent assortment, what phenotype ratios are expected among the F2 progeny from a dihybrid cross?
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How many different combinations of alleles are possible among the gametes produced by an individual that is heterozygous for three separate genes?
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Which phenomenon is a consequence of independent assortment?
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The 9:3:3:1 ratio exhibited in the F2 generation of a dihybrid cross is a genotypic ratio.
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If a pea plant is heterozygous for two genes, what proportion of the pollen produced by this plant should have the genotype PT?
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What are the genotypes of the parental plants that produce the offspring of 1/2 tall, white and 1/2 tall, violet?
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What are the genotypes of the parental plants that produce the offspring of 1/4 tall violet, 1/4 tall white, 1/4 dwarf violet, and 1/4 dwarf, white?
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What are the genotypes of the parental plants that produce the given offspring phenotype ratios from a tall, violet x tall, violet cross?
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What are the genotypes of the parental plants that produce the offspring phenotype ratios of 3/8 tall white, 3/8 tall violet, 1/8 dwarf, violet, 1/8 dwarf, white?
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What proportion of the offspring would you expect to be heterozygous for all three traits if flies that are heterozygous for all three traits are crossed?
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What proportion of the offspring would you expect to have straight wings, sparkling eyes and tan bodies if flies that are heterozygous for all three traits are crossed?
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If flies that are heterozygous for all three traits are crossed with flies that are homozygous recessive for all three traits, what proportion of the offspring would you expect to be heterozygous for all three traits?
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Study Notes
Dihybrid and Trihybrid Crosses Overview
- A plant heterozygous for four genes can produce 16 different gametes.
- In Guinea pigs, genotype SsRrbb can produce gametes SRb, Sri, sRb, and srb.
- Rabbit cross: male (llBb) with short, black fur and female (Llbb) with long, white fur results in a variety of offspring phenotypes.
Gamete Combinations and Phenotypic Ratios
- SSRRbb can produce gametes SRb.
- ssRrBB can produce gametes srB, sRB.
- SsRrbb can produce gametes sRb, srb, Srb, and SRb.
- SsRrBb can produce gametes srb, sRB, srB, SRB, sRb, SrB, SRb, and Srb.
Mendel's Laws and Ratios
- Expected phenotypic ratio in F2 progeny from a dihybrid cross is 9:3:3:1.
- An individual heterozygous for three genes can produce 8 different combinations of alleles.
- Independent assortment leads to a phenotypic ratio of 9:3:3:1 in dihybrid crosses.
True/False and Proportions
- The 9:3:3:1 ratio in F2 is a phenotypic, not genotypic, ratio.
- Proportion of PT genotype in pollen from heterozygous plant (PpTt) is approximately 1/4.
Plant Cross Examples
- Parental cross: tall, violet (DDWw) x tall, white (Ddww) produces offspring ratios of tall and white traits.
- Cross of tall, violet (DdWw) and dwarf, white (ddww) results in a quarter for each phenotype.
- Tall, violet (DdWw) x tall, violet (DdWw) leads to prominent 9/16 tall, violet offspring among other phenotypes.
- A cross of tall, violet (DdWw) with tall, white (Ddww) yields a mix of tall and dwarf offspring.
Fly Cross Experiments
- Crossing heterozygous flies for three traits results in 1/8 offspring being heterozygous for all three traits.
- Expected proportion for offspring with straight wings, sparkling eyes, and tan bodies from heterozygous crosses is 9/64.
- Crosses between heterozygous and homozygous recessive flies also yield 1/8 heterozygous traits.
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Description
Explore the complexities of dihybrid and trihybrid crosses in this quiz. Understand how different genotypes produce various gametes and the expected phenotypic ratios resulting from these genetic combinations. Test your knowledge on Mendel's laws and apply your understanding to real scenarios involving plant and animal genetics.
