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Questions and Answers
What did Alfred Sturtevant use the frequency of recombination between gene pairs for?
What did Alfred Sturtevant use the frequency of recombination between gene pairs for?
In Morgan's experiments, which gene pair showed very low recombination?
In Morgan's experiments, which gene pair showed very low recombination?
What is the significance of genetic maps in relation to whole genome sequencing?
What is the significance of genetic maps in relation to whole genome sequencing?
What did Morgan's student, Alfred Sturtevant, 'map' on chromosomes?
What did Morgan's student, Alfred Sturtevant, 'map' on chromosomes?
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Which of the following traits did Mendel primarily study?
Which of the following traits did Mendel primarily study?
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In Morgan's experiments, which gene pair showed higher recombination?
In Morgan's experiments, which gene pair showed higher recombination?
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What term is used to describe a plant that is heterozygous for genes controlling one character?
What term is used to describe a plant that is heterozygous for genes controlling one character?
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What is the purpose of a test cross in genetics?
What is the purpose of a test cross in genetics?
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Why is it not possible to predict the genotypic composition of a tall plant by just looking at its phenotype?
Why is it not possible to predict the genotypic composition of a tall plant by just looking at its phenotype?
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When tall (TT) and dwarf (tt) plants produce gametes, how do the alleles of the parental pair separate?
When tall (TT) and dwarf (tt) plants produce gametes, how do the alleles of the parental pair separate?
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In the context of genetic crosses, what is the result when a tall (TT) plant is crossed with a dwarf (tt) plant?
In the context of genetic crosses, what is the result when a tall (TT) plant is crossed with a dwarf (tt) plant?
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In a test cross, what type of organism is typically crossed with the recessive parent?
In a test cross, what type of organism is typically crossed with the recessive parent?
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What did Mendel cross to perform a test cross in his experiments?
What did Mendel cross to perform a test cross in his experiments?
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What is the probability of a gamete from a heterozygous Tt plant containing the 'T' allele?
What is the probability of a gamete from a heterozygous Tt plant containing the 'T' allele?
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In Mendel's experiments, what does the Punnett Square help visualize?
In Mendel's experiments, what does the Punnett Square help visualize?
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Why did Mendel propose two general rules based on his observations on monohybrid crosses?
Why did Mendel propose two general rules based on his observations on monohybrid crosses?
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Which British geneticist developed the Punnett Square?
Which British geneticist developed the Punnett Square?
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What can be predicted about the genotype of the test organism from the progenies of a test cross?
What can be predicted about the genotype of the test organism from the progenies of a test cross?
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Study Notes
Genetic Mapping and Recombination
- Alfred Sturtevant utilized the frequency of recombination between gene pairs to create genetic maps, demonstrating the relative distances between genes on chromosomes.
- The gene pair that showed very low recombination in Morgan's experiments was the white and yellow color genes in fruit flies, indicating they are linked closely on the same chromosome.
- Genetic maps are significant for whole genome sequencing as they provide a reference framework for understanding gene location and function, aiding in the identification of genetic disorders.
Contributions of Morgan and Sturtevant
- Alfred Sturtevant mapped the locations of genes on chromosomes, contributing to the foundation of linkage mapping in genetics.
- In Morgan's experiments, the gene pair that exhibited higher recombination was the body color and wing size genes, showing they are farther apart on the chromosome.
Mendelian Genetics
- Mendel primarily studied traits such as seed shape and color, focusing on discrete phenotypic characteristics in pea plants.
- A plant that is heterozygous for genes controlling one character is called a dihybrid, showcasing different alleles for the different traits.
Test Cross Purpose
- A test cross is performed to determine the genotype of an organism with a dominant phenotype by crossing it with a homozygous recessive parent, revealing the alleles passed to the offspring.
- It is not possible to predict the genotypic composition of a tall plant (TT or Tt) based solely on phenotype because two different genotypes can result in the same tall phenotype.
Allele Separation and Cross Outcomes
- When tall (TT) and dwarf (tt) plants produce gametes, the alleles separate during meiosis, with each gamete receiving one allele from each parent.
- The result of crossing a tall (TT) plant with a dwarf (tt) plant will yield all offspring with the tall phenotype (Tt), but their exact genotype remains uncertain in all cases.
Test Cross Details
- In a test cross, the dominant phenotype organism is typically crossed with a recessive parent to determine its genotype.
- Mendel performed a test cross using true breeding recessive strains to track inheritance patterns in subsequent generations.
Genetic Probabilities and Predictive Tools
- The probability of a gamete from a heterozygous Tt plant containing the 'T' allele is 50%, as each allele has an equal chance of being passed on.
- The Punnett Square aids in visualizing the potential combinations of alleles and the resulting genotypes of offspring from genetic crosses.
- Mendel proposed two general rules (law of segregation and law of independent assortment) based on his observations of monohybrid crosses to explain hereditary patterns.
Historical Figures in Genetics
- The Punnett Square was developed by British geneticist Reginald Punnett and has become a fundamental tool in genetics.
- From the progeny of a test cross, the genotype of the test organism can be inferred, as homozygous recessive offspring will reveal the presence or absence of dominant alleles.
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Description
Test your knowledge on Mendel's test cross and how it helps in determining the genotype of tall plants in the F2 generation. Understand how the test cross helps in unraveling the genetic composition by crossing tall plants with dwarf plants.
