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Genetics

Genetics. Genes. Trait = specific characteristic that changes from one individual to another Gene = chemical factors that determine traits Found in DNA Genes for various traits are found on chromosomes Allele = different forms of a gene. Genes. Example Trait = plant height

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Genetics

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  1. Genetics

  2. Genes • Trait = specific characteristic that changes from one individual to another • Gene = chemical factors that determine traits • Found in DNA • Genes for various traits are found on chromosomes • Allele = different forms of a gene

  3. Genes • Example • Trait = plant height • Alleles (different forms of gene) • Short • Tall

  4. Genes and Dominance • Principle of Dominance = some alleles are dominant and others are recessive • Dominant alleles are generally expressed using a capital letter • Recessive alleles are usually expressed using a lower case letter • Ex. Plant height • Dominant = tall (T) • Recessive = short (t)

  5. Segregation of Alleles • Each individual contains 2 alleles for each trait (one from each parent) • During meiosis, when the number of chromosomes are reduced (diploid to haploid), gametes are produced that contain one allele for each trait • Segregation = the separation of alleles for a certain trait

  6. Segregation of Alleles • Each gamete only carries a single allele for each gene • During fertilization, two gametes fuse forming a diploid cell. • This cell contains 2 alleles for each trait.

  7. Alleles • Homozygous = individual with 2 of the same allele for a given trait • Ex. TT, tt, RR, rr • Heterozygous = individual with 2 different alleles for a given trait • Ex. Tt, Rr, Ww

  8. Alleles • Homozygous Dominant = 2 dominant alleles (ex. TT) • Homozygous Recessive = 2 recessive alleles (ex. tt) • Heterozygous = 1 dominant allele and 1 recessive allele (ex. Tt)

  9. Genotype vs. Phenotype • Genotype • The combination of alleles for a given trait • Ex. TT, Tt, tt • Phenotype • The physical appearance caused by the interaction of alleles • In general, if a dominant allele is present then the dominant condition will be shown • Ex. Tall, Short

  10. Chromosome Number • Homologous Chromosomes • Chromosomes of the same kind; hold genetic information for the same traits • Diploid (2N) (N = # of sets of chromosomes) • Contains both sets of homologous chromosomes • Has 2 sets • Haploid (N) • Contains one set of chromosomes

  11. Gamete Formation

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