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Intro. genetics


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  • 1. Chapter 9 GeneticsBy Mr. “I love winter” Chapman
  • 2. Intro. Genetics Genetics – a field of biology dedicated to understanding how characteristics are transmitted from parents to offspring (heredity). Student Characteristics?
  • 3. Genetics Terms Allele – several alternative forms of a gene; 2 alleles for hair color (brown and black hair) Ex. Bb
  • 4. Genetic Terms Pollination – occurs when pollen grains (sperm) produced by anther reach the female reproductive part (stigma).
  • 5. Genetic Terms Self-pollination – when pollen reaches female part on the same plant.
  • 6. Genetic Terms Cross-pollination – is the transfer of pollen between two different plants.
  • 7. Genetics Gregor Mendel the father of genetics. Gregor Mendel experimented with peas: He observed different traits in peas  Ex. Plant height, flower position, pod color, seed color and flower color He noticed that purple flowered pea plants produced purple and white flowered pea plants.. why?
  • 8. Mendel’s Experiments Began by growing plants that were pure for a trait  they always produce offspring with that trait (P1 Generation)  Ex. Purple flowers purple flowers Cross pollinate two different traits  their offspring is the F1 Generation  Purple and white flowers F1 Generation self pollinated  their offspring is the F2 Generation
  • 9. Mendel’s ExperimentMendel’s Conclusions1. Dominant and Recessive Traits Dominant allele – an allele that dominates or masks the other allele  Ex. When a green pod allele (G) is with a yellow pod allele (g) the green pod will result Recessive allele – an allele that has not observable effect on an organism’s appearance when paired with a dominant allele  Ex. The yellow pod allele
  • 10. Mendel’s Conclusions 2. The Law of Segregation  paired alleles separate during the formation of reproductive cells (gametes)
  • 11. Mendel’s Experiment 3. The Law of Independent Assortment  the alleles for different characteristics are distributed to gametes independently A yellow pod could appear in plants with purple or white flowers
  • 12. Genetic Terms Genotype – the genetic make-up of an organism.  Ex. the alleles PP, Pp or pp are three different genotypes Phenotype – the appearance of an organism  Ex. Purple flowers or White flowers
  • 13. Example Purple allele is P White allele is p Genotype: PP or Pp and pp Phenotype: Purple or white
  • 14. Genetic Terms Genotype – the genetic make-up of an organism.  Ex. the alleles PP, Pp or pp are three different genotypes Phenotype – the appearance of an organism  Ex. PP and Pp are purple flowers, pp is white Homozygous – the two alleles are the same  Ex. PP or pp Heterozygous – the two alleles are different Ex. Pp
  • 15. Genetic Terms Monohybrid cross – a cross between individuals that involves one pair of traits  Ex. crossing a plant with all purple flowers with a plant with all white flowers.
  • 16. Genetic Terms A Punnett Square is a handy dandy device for predicting the results of a monohybrid cross.
  • 17. Sex Chromosomes Sex Determination Thomas Morgan (early 1900’s) bred fruit flies and observed the sex chromosomes  Females XX  Males XY
  • 18. Sex Chromosomes Homologous chromosomes separate during Meiosis I  Male gametes have either X or Y  Female gametes have X When fertilization occurs who determines the sex of the offspring?
  • 19. Sex Chromosomes What is the chance that the offspring will be female and what is the chance that the offspring will be male? Sex Linkage – the presence of a gene on the sex chromosome X-linked genes – genes on the X chromosome