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Questions and Answers
In a scenario where a plant with an unknown genotype, but expressing a dominant phenotype, is crossed with a homozygous recessive plant, and the offspring show a 1:1 ratio of dominant to recessive phenotypes, what can be inferred about the genotype of the unknown plant parent?
In a scenario where a plant with an unknown genotype, but expressing a dominant phenotype, is crossed with a homozygous recessive plant, and the offspring show a 1:1 ratio of dominant to recessive phenotypes, what can be inferred about the genotype of the unknown plant parent?
- The unknown parent is homozygous dominant.
- The results do not provide enough information to determine the genotype of the unknown parent.
- The unknown parent is heterozygous. (correct)
- The unknown parent is homozygous recessive.
If a homozygous dominant plant is crossed with a plant that is heterozygous, what is the expected frequency of genotypes in the offspring?
If a homozygous dominant plant is crossed with a plant that is heterozygous, what is the expected frequency of genotypes in the offspring?
- 50% homozygous dominant, 50% heterozygous (correct)
- 100% heterozygous
- 75% homozygous dominant, 25% heterozygous
- 25% homozygous dominant, 50% heterozygous, 25% homozygous recessive
In a dihybrid cross, if both parents are heterozygous for two traits (e.g., SsYy), what is the probability of producing offspring that are homozygous recessive for both traits (ssyy)?
In a dihybrid cross, if both parents are heterozygous for two traits (e.g., SsYy), what is the probability of producing offspring that are homozygous recessive for both traits (ssyy)?
- 9/16
- 1/16 (correct)
- 1/4
- 3/16
In a monohybrid cross, if two heterozygous individuals (Pp) are crossed, what is the expected ratio of phenotypes in their offspring?
In a monohybrid cross, if two heterozygous individuals (Pp) are crossed, what is the expected ratio of phenotypes in their offspring?
What is the purpose of performing a test cross?
What is the purpose of performing a test cross?
In the context of genetics, what does the term 'genotype' refer to?
In the context of genetics, what does the term 'genotype' refer to?
In a dihybrid cross where the phenotype ratio is 9:3:3:1, what does this ratio signify?
In a dihybrid cross where the phenotype ratio is 9:3:3:1, what does this ratio signify?
What does it mean when an allele is described as 'dominant'?
What does it mean when an allele is described as 'dominant'?
How does a dihybrid cross differ from a monohybrid cross?
How does a dihybrid cross differ from a monohybrid cross?
If purple flowers are dominant (P) and white flowers recessive (p), what genotypes would result in a plant with white flowers?
If purple flowers are dominant (P) and white flowers recessive (p), what genotypes would result in a plant with white flowers?
Flashcards
Genotype
Genotype
The genetic makeup of an organism, all the genes and alleles.
Phenotype
Phenotype
The observable characteristics of an organism resulting from the interaction of its genotype with the environment.
Homozygous
Homozygous
Having two identical alleles for a particular gene.
Heterozygous
Heterozygous
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Monohybrid Cross
Monohybrid Cross
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First Filial Generation (F1)
First Filial Generation (F1)
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Second Filial Generation (F2)
Second Filial Generation (F2)
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Test Cross
Test Cross
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Dihybrid Cross
Dihybrid Cross
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9:3:3:1 Phenotype Ratio
9:3:3:1 Phenotype Ratio
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Study Notes
- Parents contribute to offspring
- Genotype refers to genetic characteristics
- Phenotype refers to observed traits
- Uppercase signifies the dominant allele copy
- Lowercase signifies the recessive allele copy
- Homozygous alleles are the same
- Heterozygous alleles are different
Monohybrid Crosses
- Parents are on the outside of the Punnett square
- Offspring are on the inside of the Punnett square
- First filial generation is when you breed the offspring of the parent generation
- Second filial generation is when you breed the offspring of the first generation
- 100% of offspring are tall when both parents are heterozygous, one dominant, one recessive
- Frequency of genotypes: 100% heterozygous
- Frequency of phenotypes: 100% tall
Mendel's Experiment Results
- Uppercase P = purple
- Lowercase p = white
- When crossing purple and white flowered plants, first generation offspring ended up purple (Pp) and heterozygous
- Crossing the first generation (Pp x Pp) yielded: -One quarter homozygous dominant (PP), appearing purple -One half heterozygous (Pp), appearing purple -One quarter homozygous recessive (pp), appearing white
- Genotype frequency in the second generation is 1:2:1 (PP:Pp:pp)
- Phenotype frequency is three purple to one white
Test Cross
- Used to determine the genotype of an individual with a dominant phenotype when the other parent's genotype is known
- Example parent cross: Mom (pp - white) + Dad (unknown) = all purple offspring
- Daddy can either be PP or Pp
- If unknown parent is homozygous dominant (PP), all offspring are purple and heterozygous (Pp)
- If unknown parent is heterozygous (Pp), half offspring will be purple (Pp) and half will be white (pp)
- If a cross with unknown yielded 1/2 purple 1/2 white result, parents genotype is able to be determined
Dihybrid Crosses
- Involves two characteristics at the same time
- Example: Tall and purple plant crossed with another tall and purple plant
- Phenotype frequency is 9:3:3:1 (tall & purple : short & purple : tall & white : short & white)
- Monohybrid cross second generation ratio is 3:1
- Dihybrid cross results in a 9:3:3:1 ratio
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