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History of Genetics: Aristotle to Modern Times
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History of Genetics: Aristotle to Modern Times

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Questions and Answers

What was the historical understanding of heredity before the development of modern genetics?

  • The concept of natural selection
  • The blending of traits between parents (correct)
  • The inheritance of acquired characteristics
  • The role of mutations in variation

    • What was the focus of Morgan's research in genetics?

  • The investigation of natural selection
  • The study of biometrics
  • The analysis of mutations in fruit flies (correct)
  • The exploration of continuous variation

    • What was the significance of the white-eyed fly in Morgan's research?

  • It showed the relationship between genetics and cell biology
  • It exhibited a sex-linked gene (correct)
  • It represented a continuous variation
  • It demonstrated the concept of natural selection

    • What was the contribution of Fisher's work in genetics?

    <p>The finding that continuous variation is due to combined effects of several genes</p> Signup and view all the answers

    What is the result of recurrent mutation and selection against variation?

    <p>A decrease in genetic variation in a population</p> Signup and view all the answers

    What is the term for the loss of genetic variation in a population over time?

    <p>Genetic drift</p> Signup and view all the answers

    What is the role of selection in maintaining genetic variation in a population?

    <p>It can prevent the loss of variation</p> Signup and view all the answers

    What was the focus of the Biometricians in the early days of genetics?

    <p>The analysis of variations in characters like height and milk yield</p> Signup and view all the answers

    What was the significance of Morgan's choice of fruit flies in his research?

    <p>They were easy to breed and study</p> Signup and view all the answers

    What was the historical context of the development of modern genetics?

    <p>The work of Aristotle and the Western scientific world</p> Signup and view all the answers

    What is the result of faster mutations and stronger selection against them?

    <p>A decrease in mutant alleles</p> Signup and view all the answers

    What is the advantage of being a heterozygote?

    <p>Having a higher fitness than homozygotes</p> Signup and view all the answers

    What is the result of negative frequency-dependent selection?

    <p>The rarer alleles become more common</p> Signup and view all the answers

    What is the result of gene flow between two populations?

    <p>An increase in variation in both populations</p> Signup and view all the answers

    What is the characteristic of a sharp cline?

    <p>Strong selection and low dispersal</p> Signup and view all the answers

    What is the result of fluctuating selection?

    <p>An increase in variation in the population</p> Signup and view all the answers

    What was the importance of the discovery of isozymes in 1957?

    <p>It led to the discovery of molecular genetics</p> Signup and view all the answers

    What is the main argument against the genetic load argument?

    <p>It requires too much death to be plausible</p> Signup and view all the answers

    What is the prediction of the neutral theory?

    <p>The evolution rate is equal to the mutation rate</p> Signup and view all the answers

    What is the result of very slow evolution?

    <p>Sequence conservation</p> Signup and view all the answers

    What was the primary focus of the Biometricians in their research?

    <p>Examining the variation in characters such as height and milk yield</p> Signup and view all the answers

    What was the significance of Morgan's choice of fruit flies in his research?

    <p>They were easy to breed and had short generations</p> Signup and view all the answers

    What was the primary contribution of Fisher's work to the field of genetics?

    <p>Showing that continuous variation could be due to the combined effects of several genes</p> Signup and view all the answers

    What is the result of recurrent mutation and selection against variation?

    <p>A decrease in genetic variation over time</p> Signup and view all the answers

    What is the main effect of genetic drift on a population?

    <p>It leads to a decrease in genetic variation</p> Signup and view all the answers

    What is the main effect of selection on genetic variation in a population?

    <p>It decreases genetic variation</p> Signup and view all the answers

    What was the significance of Aristotle's work in the historical development of genetics?

    <p>He proposed the blending of traits between parents</p> Signup and view all the answers

    What was the significance of Morgan's research on fruit flies?

    <p>He made connections between genetics and cell biology</p> Signup and view all the answers

    What is the effect of combined effects of several genes on continuous variation?

    <p>It leads to an increase in variation</p> Signup and view all the answers

    What is the effect of genetic variation on the adaptation of a population?

    <p>It increases the adaptation of a population</p> Signup and view all the answers

    What is the primary factor that determines the amount of variation expected in a population under the neutral theory?

    <p>Mutation rate and population size</p> Signup and view all the answers

    What is the consequence of very fast evolution in a sequence?

    <p>It is currently adapting</p> Signup and view all the answers

    What is the role of heterozygote advantage in maintaining genetic variation?

    <p>It maintains variation at a locus by making heterozygotes more fit</p> Signup and view all the answers

    What is the outcome of gene flow between two populations with different adaptations?

    <p>The maintenance of variation in the population</p> Signup and view all the answers

    What is the consequence of a sharp cline in allele frequency?

    <p>Strong selection and low dispersal</p> Signup and view all the answers

    What is the primary problem with the genetic load argument?

    <p>It assumes that all variation is maintained by selection</p> Signup and view all the answers

    What is the result of fluctuating selection on genetic variation?

    <p>It maintains genetic variation in the population</p> Signup and view all the answers

    What is the significance of the discovery of isozymes in 1957?

    <p>It showed that genetic variation is widespread</p> Signup and view all the answers

    What is the prediction of the neutral theory regarding the evolution rate?

    <p>It is equal to the mutation rate</p> Signup and view all the answers

    What is the role of mutation in shaping genetic variation under the neutral theory?

    <p>It creates new alleles that drift to a frequency of 1 or 0</p> Signup and view all the answers

    Study Notes

    Historical Background of Genetics

    • Genetics is the study of heredity and variation
    • Aristotle and the Western scientific world thought in terms of blending of traits/bloods between parents, and sometimes inheritance of acquired characteristics

    Early Developments in Genetics

    • Thomas Morgan worked on mutations and how they were inherited, which was initially seen as evidence against Darwin
    • There were two factions: Medalists (mutation is the important process) and Biometricians (variations in characters like height/milk yield)
    • Morgan chose fruit flies and made connections between genetics and cell biology
    • Flies around the world are still descended from his original population

    Understanding Variation

    • Mutations and variations were carefully catalogued, crossed, and observed
    • A fly with white eyes had a sex-linked gene
    • Fisher's work brought the two factions together, showing that continuous variation could be due to combined effects of several genes

    Factors Affecting Variation

    • Recurrent mutation and selection can lead to a situation where mutation creates rare alleles, and selection removes them
    • Heterozygote advantage maintains variation at a locus, making it better to be Aa than AA or aa
    • Negative frequency-dependent selection can occur, where the rarer alleles have rarity value
    • Gene flow can maintain variations between areas with different environments
    • Fluctuating selection can maintain variation by favouring different alleles in different generations

    Advances in Molecular Genetics

    • 1957: discovery of isozymes and development of molecular genetics
    • Protein sequencing and DNA sequencing showed even more variation, including at silent sites
    • The genetic load argument suggests that the explanation of variation being maintained by selection is implausible

    Neutral Theory

    • Kimura calculated the evolution rate, which equals the mutation rate, if all variation is neutral
    • The amount of variation expected in a population depends on mutation rate and population size
    • The neutral theory gives us a null hypothesis
    • Very slow evolution is called sequence conservation or purifying selection, or sometimes negative selection
    • Very fast evolution might mean the sequence is currently adapting

    Historical Background of Genetics

    • Genetics is the study of heredity and variation
    • Aristotle and the Western scientific world thought in terms of blending of traits/bloods between parents, and sometimes inheritance of acquired characteristics

    Early Developments in Genetics

    • Thomas Morgan worked on mutations and how they were inherited, which was initially seen as evidence against Darwin
    • There were two factions: Medalists (mutation is the important process) and Biometricians (variations in characters like height/milk yield)
    • Morgan chose fruit flies and made connections between genetics and cell biology
    • Flies around the world are still descended from his original population

    Understanding Variation

    • Mutations and variations were carefully catalogued, crossed, and observed
    • A fly with white eyes had a sex-linked gene
    • Fisher's work brought the two factions together, showing that continuous variation could be due to combined effects of several genes

    Factors Affecting Variation

    • Recurrent mutation and selection can lead to a situation where mutation creates rare alleles, and selection removes them
    • Heterozygote advantage maintains variation at a locus, making it better to be Aa than AA or aa
    • Negative frequency-dependent selection can occur, where the rarer alleles have rarity value
    • Gene flow can maintain variations between areas with different environments
    • Fluctuating selection can maintain variation by favouring different alleles in different generations

    Advances in Molecular Genetics

    • 1957: discovery of isozymes and development of molecular genetics
    • Protein sequencing and DNA sequencing showed even more variation, including at silent sites
    • The genetic load argument suggests that the explanation of variation being maintained by selection is implausible

    Neutral Theory

    • Kimura calculated the evolution rate, which equals the mutation rate, if all variation is neutral
    • The amount of variation expected in a population depends on mutation rate and population size
    • The neutral theory gives us a null hypothesis
    • Very slow evolution is called sequence conservation or purifying selection, or sometimes negative selection
    • Very fast evolution might mean the sequence is currently adapting

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    Description

    Explore the historical background of genetics, from Aristotle's ideas to the modern understanding of heredity and variation. Learn about the contributions of Morgan and the debates between Medalists and Biometricians.

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