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Questions and Answers
What is the main focus of Mendel's experiments?
What is the main focus of Mendel's experiments?
What are dominant traits?
What are dominant traits?
Traits that appear in the next generation when pure contrasting traits are crossed.
What does the law of segregation state?
What does the law of segregation state?
Alleles for a trait separate during the formation of gametes.
Which of the following describes incomplete dominance?
Which of the following describes incomplete dominance?
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In codominance, both traits show up in the offspring's phenotype.
In codominance, both traits show up in the offspring's phenotype.
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The interaction of different gene loci, such that one gene locus masks or suppresses the expression of another, is called ______.
The interaction of different gene loci, such that one gene locus masks or suppresses the expression of another, is called ______.
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What are linked genes?
What are linked genes?
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What does the law of independent assortment state?
What does the law of independent assortment state?
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What are multiple alleles?
What are multiple alleles?
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Organisms that have two different alleles for a particular trait are said to be:
Organisms that have two different alleles for a particular trait are said to be:
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Which of the following statements below is true about recessive alleles?
Which of the following statements below is true about recessive alleles?
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In mango plants, tall is dominant to short. If a homozygous tall mango plant is crossed with a heterozygous plant, what is the probability that the offspring will be short?
In mango plants, tall is dominant to short. If a homozygous tall mango plant is crossed with a heterozygous plant, what is the probability that the offspring will be short?
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In eggplants, the allele for purple fruit (P) is dominant to the allele for green fruit (p). A plant with genotype PP is crossed with a plant with genotype Pp. What are the expected genotype percentages in the offspring of this cross?
In eggplants, the allele for purple fruit (P) is dominant to the allele for green fruit (p). A plant with genotype PP is crossed with a plant with genotype Pp. What are the expected genotype percentages in the offspring of this cross?
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If the phenotypic ratio of a dihybrid cross population with 16,000 individuals is 9:3:3:1, how many individuals have at least one dominant allele?
If the phenotypic ratio of a dihybrid cross population with 16,000 individuals is 9:3:3:1, how many individuals have at least one dominant allele?
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A red flowered plant (RR) breeds with a white flowered plant (WW). The gene for petal color in these plants expresses incomplete dominance. What percentage of the offspring will have pink (RW) flowers?
A red flowered plant (RR) breeds with a white flowered plant (WW). The gene for petal color in these plants expresses incomplete dominance. What percentage of the offspring will have pink (RW) flowers?
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In some Gumamela flowers a cross is made between red (R) and white (W) flowers. The offspring shows speckled flowers (RW) that show both colors. What type of inheritance is this?
In some Gumamela flowers a cross is made between red (R) and white (W) flowers. The offspring shows speckled flowers (RW) that show both colors. What type of inheritance is this?
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What is the phenotypic frequency of the offspring when two speckled red/white flowers are crossed?
What is the phenotypic frequency of the offspring when two speckled red/white flowers are crossed?
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In which inheritance pattern do heterozygous individuals express the dominant allele and completely mask the effect of the recessive allele?
In which inheritance pattern do heterozygous individuals express the dominant allele and completely mask the effect of the recessive allele?
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Which of the following statements could be considered as incomplete dominance inheritance?
Which of the following statements could be considered as incomplete dominance inheritance?
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Study Notes
Inheritance of Plant Traits
- Gregor Mendel's experiments with garden peas laid the foundation for understanding heredity.
- He established the principles of inheritance by observing patterns of trait transmission across generations.
- Mendel's experiments involved true-breeding parents, hybridization, and self-pollination of hybrids.
- True breeding refers to self-fertilization of parent stocks to determine if traits are passed on to offspring.
- Hybridization involves cross-fertilization of true-breeding parents, producing hybrids.
- Self-pollination of hybrids generates a segregating population (F2 generation) where traits are further analyzed.
Basic Laws of Inheritance
- Law of Dominance: When contrasting traits are crossed, one trait (dominant) masks the other (recessive). Offspring inherit a dominant allele, showcasing only the dominant trait.
- Law of Segregation: During gamete formation, the two alleles responsible for a trait separate from each other. Alleles recombine during fertilization, determining the offspring's genotype.
- Law of Independent Assortment: Alleles for different traits are distributed independently during sex cell formation.
Extensions of Inheritance Laws
- Incomplete Dominance: Neither trait is completely dominant over the other. Hybrid offspring display a blended phenotype, demonstrating a combination of both alleles.
- Codominance: Both traits are dominant and expressed together in the offspring's phenotype.
- Multiple Alleles: When three or more alleles exist for a trait, these are called multiple alleles. This occurs when several variations of a gene are present within a population.
- Linked Genes: Genes physically close together on the same chromosome are likely inherited together.
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Epistasis: Interactions between different gene loci where one locus masks or suppresses the expression of another gene locus. There are two types:
- Dominant Epistasis: The controlling allele masks another allele.
- Recessive Epistasis: The controlling allele is recessive, masking the other allele only when homozygous recessive.
Genotype & Phenotype
- Genotype: the genetic makeup of an organism for a trait (e.g., RR, Rr, rr)
- Phenotype: the physical expression of a trait, determined by the genotype (e.g., red, white)
Alleles
- Alleles: alternative forms of a gene (like 'flavors' of a trait)
- Homozygous genotype: a gene combination with two identical alleles (either both dominant or both recessive) (e.g., BB or bb); also called pure
- Heterozygous genotype: a gene combination with one dominant and one recessive allele (e.g., Bb); also called hybrid
Recessive Alleles
- Recessive alleles are expressed only when two copies of the recessive allele are present (homozygous recessive)
Dominant Alleles
- Dominant alleles are expressed even in the presence of a recessive allele (heterozygous)
Incomplete Dominance
- A type of inheritance where heterozygous individuals express a phenotype that is intermediate between the two homozygous phenotypes.
- Example: In a flower with incomplete dominance, a homozygous red flower (RR) crossed with a homozygous white flower (WW) will produce offspring with pink flowers (RW).
Codominance
- A type of inheritance where both alleles are expressed equally in the heterozygous phenotype.
- Example: In a Gumamela flower, if a red flower (R) is crossed with a white flower (W), the offspring will have speckled flowers (RW) showing both red and white colors.
Phenotypic Frequency
- Phenotypic frequency is the proportion of individuals in a population with a specific phenotype.
- In a dihybrid cross with a phenotypic ratio of 9:3:3:1, 15,000 out of 16,000 individuals will have at least one dominant allele.
Complete Dominance
- A type of inheritance where the heterozygous individuals express the dominant allele and completely mask the effect of the recessive allele.
- Example: In a plant with complete dominance, a homozygous tall plant (TT) crossed with a homozygous short plant (tt) will produce offspring that are all tall (Tt).
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Description
Explore the foundational concepts of inheritance through Gregor Mendel's groundbreaking experiments with garden peas. This quiz covers true-breeding, hybridization, and the basic laws of inheritance, including dominance and segregation. Test your understanding of these principles and how traits are transmitted through generations.
