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GENETICS

GENETICS. GENETICS. Genetics = study of how characteristics are transmitted from parents to offspring Father of Genetics: Gregor Mendel studied pea plants. GENETICS. Heredity - transmission of characteristics from parents to offspring. GENETICS.

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GENETICS

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  1. GENETICS

  2. GENETICS • Genetics = study of how characteristics are transmitted from parents to offspring • Father of Genetics: Gregor Mendel • studied pea plants

  3. GENETICS Heredity- transmission of characteristics from parents to offspring

  4. GENETICS Traits- genetic characteristic (height, flower color, etc)

  5. GENETICS Gene- a segment of DNA on a chromosome that controls a particular trait

  6. GENETICS RR or Rr rr Note that most human traits are multi-allele. Even something as simple as this may actually be due to the expression of several genes. • Allele- alternative forms of a gene • Example: gene = tongue rolling allele = can roll (R), cannot roll (r) • Alleles represented by letters: • Capital for dominant alleles (A, T, H, etc) • Lower case for recessive alleles (a, t, h, etc)

  7. GENETICS Dominant- masks the presence of another allele Recessive - is masked by the presence of another allele

  8. GENETICS • Phenotype- the appearance of an organism or how the trait is expressed. • pink flowers, albino, tall, etc.

  9. GENETICS • Genotype- the genetic make-up of an organism. • What the DNA says • Aa, AA, aa • 2 alleles per gene • One from mom, one from dad

  10. GENETICS • Homozygous- both alleles for a trait are the same. • Can be homozygous dominant RR or homozygous recessive rr

  11. GENETICS Heterozygous- both alleles are different. Ex. Rr (the dominant allele is usually all we can see in phenotype)

  12. Mendel’s Laws The Law of Segregation- a pair of alleles is segregated, or separated during the formation of gametes

  13. Mendel’s Laws • The Law of Independent Assortment- alleles for different characteristics are distributed to gametes individually • (ex. Hair color is separate from eye color; height from intelligence, etc)

  14. Mendel’s Laws The Law of Dominance- a trait controlled by a recessive factor has no observable effect on an organism’s appearance when it is paired with a trait controlled by a dominant factor

  15. Monohybrid Cross • Cross one trait at a time to see possible results • First generation = P • Second generation = F1 • Third generation = F2 • Fourth generation = F3 • Etc • (your parents = what you start with)

  16. Monohybrid Cross Father Mother BB bb B = Black b = Brown Show crosses with a PunnettSquare

  17. Mothers Alleles BB x bb b b Bb B Bb Father’s Alleles Bb B Bb

  18. Genotype: 100% “Bb” Phenotype: 100% Black

  19. Mothers Alleles Bb x Bb B b Bb BB B Father’s Alleles bb Bb b Note that Mendel did his experiment using plants. Therefore he could breed two individuals from his P generation together to produce F1. When breeding animals, it is generally unwise to breed siblings together as it can lead to genetic illness.

  20. Predicted Genotypes: 25% BB, 50% Bb, 25% bb Predicted Phenotypes: 75% Black, 25% Brown Note the yellow puppies. In Labradors, there are actually 2 genes that control coat color. Black vs. Brown is one gene. The other gene codes for the creation of coat color. When this gene is homozygous recessive, you get yellow puppies (no coat color).

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