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11 – Introduction to Genetics. The Work of Gregor Mendel. Inheritance other than $$$$ How did things get passed on? Genetics – the scientific study of heredity Mendel, peas and his work Long overlooked. The Role of Fertilization. Male and Female Parts

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The work of gregor mendel
The Work of Gregor Mendel

  • Inheritance other than $$$$

  • How did things get passed on?

    • Genetics – the scientific study of heredity

  • Mendel, peas and his work

    • Long overlooked


The role of fertilization
The Role of Fertilization

  • Male and Female Parts

    • Fertilization – joining of reproductive cells

    • Self-pollination

      • True breeding

    • Trait

      • Cross Breeding

        • Male parts gone

    • Hybrids


Genes and alleles
Genes and Alleles

  • P1 and F1 generations

  • Disappearance of traits

  • Parent to offspring by genes.

    • Mendel called them factors

  • Single gene trait (ex. Tall vs. Short)

  • Alleles – forms of a gene


Dominant and recessive alleles
Dominant and Recessive Alleles

  • Principle of Dominance

    • Mendel’s second conclusion

  • One dominant allele

    • Organism shows that trait

  • Recessive Alleles

    • Only show when dominant is not present


Segregation
SEGREGATION

  • What happened to the other trait?

    • Was it still in the F1?

  • Did an F2 cross

    • Trait reappeared

  • Mendel assumed Dominance masks


F1 cross and gametes
F1 Cross and Gametes

  • One trait separated from the other

    • Segregation

    • During gamete formation

      • Follow this chart



11 2 applying mendel s principles probability and punnett squares
11.2 Applying Mendel’s Principles – Probability and Punnett Squares

  • Probability – likelihood that an event would occur.

    • Mendel analyzed his data

    • Found probability

  • Segregation and Outcomes –

    • Alleles segregate during gamete formation (haploid)

    • Homozygous vs. Heterozygous


Probabilities averages genotype and phenotype
Probabilities, Averages, Genotype and Phenotype

  • Probabilities predict the average outcome

  • Genetic makeup vs. observable characteristics

    • Genotype vs. Phenotype

  • Punnett Squares

    • Uses math to predict


Independent assortment
Independent Assortment

  • Does segregation of one pair affect other pairs?

    • Two factor (dihybrid) cross

    • Followed two traits

      • F1

      • F2

      • Independent Assortment

        • Some genes separate independent of each other


Summary of mendel
Summary of Mendel

  • Characteristics are determined by genes and passed from parents

  • If there are two or more forms of alleles some may be dominant or recessive

  • Most adults have two copies of each gene (one from mom and one from dad) and the segregate during gamete formation

  • Alleles usually segregate independent of each other


Summary
Summary

  • Thomas Hunt Morgan

    • Showed that the same principles apply to animals

    • Fruit Fly (Drosophila melanogaster)



Beyond dominant and recessive
Beyond Dominant and Recessive

  • Incomplete Dominance

    • Traits blend

  • Codominance

    • Both traits show

  • Multiple Allele

    • More than two alleles

  • Polygenic

    • Several Genes involved


Genes and environment
Genes and Environment

  • Environment can affect gene expression

    • Phenotype is determined by genotype and environment

    • Western White Butterfly

      • Pigment changes

      • Why?



Chromosome number
Chromosome Number

  • Diploid Cells

    • Homologous pairs

      • Diploid (2N)

    • Inherited from each parent

    • Segregate during gamete formation

  • Haploid Cells

    • Single set of chromosomes


Phases of meiosis
Phases of Meiosis

  • Meiosis

    • Chromosome # cut by half

  • Prophase I

    • Tetrad

    • Crossing over

  • Metaphase I and Anaphase I

    • Paired homologous chromosomes line up


Phases of meiosis1
Phases of Meiosis

  • Telophase I and Cytokinesis

    • Results in 2 daughter cells

    • Haploid in number

  • Prophase II

    • No tetrads

  • Metaphase II, Anaphase II, Telophase II and Cytokinesis

    • Similar to Meiosis I but four daughter cells result (gametes) (zygote)


Comparing meiosis and mitosis
Comparing Meiosis and Mitosis

  • Replication and Separation of Genetic Material

    • Mitosis

      • Replicate once, divide once (single chromosomes lined up, full set of chromosomes at end

    • Meiosis

      • Replicate once, divide twice (pairs lined up), half the number of chromosomes at end.


Gene linkage and gene maps
Gene Linkage and Gene Maps

  • Gene Linkage (Thomas Hunt Morgan)

    • Traits assort independently IF

      • they are on different chromosomes or

      • Very far apart on same chromosome

    • If they are fairly close on the same chromosome, they are LINKED

  • Distance apart on the chromosome is key

    • The closer the genes are, the more linked they are

  • Maps are made based on how often crossing over is observed


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