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Dominant vs. Recessive and Genotype vs. Phenotype

Dominant vs. Recessive and Genotype vs. Phenotype . Yes: No:. Do you have a widow’s peak?. Yes: No:. Do you have unattached earlobes?. Yes: No:. Can roll your tongue?. These are all DOMINANT traits. We tend to see these traits more often in society. Why is that?

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Dominant vs. Recessive and Genotype vs. Phenotype

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  1. Dominant vs. Recessive andGenotype vs. Phenotype

  2. Yes: No: Do you have a widow’s peak? • Yes: No: Do you have unattached earlobes? • Yes: No: Can roll your tongue?

  3. These are all DOMINANT traits. • We tend to see these traits more often in society. • Why is that? • YOU WILL LEARN TODAY!

  4. Things we already know: • Chromosomes are made up of ______________ • Genes code for ____________ • A pair of genes that interact to code for a trait are called ________ GENES TRAITS GENE PAIRS OR ALLELES

  5. Skin tone is an example of a trait that is controlled by multiple genes. That’s why we have a variety of skin tones in the world!

  6. So let’s focus on some traits that are only controlled by ONE gene. • These are the traits that you either have one form or the other. • There’s no in-between. • What are some examples of traits controlled by only ONE gene (from your HW!)

  7. Hairline: Two forms? Widow’s peak vs. straight Handedness: Two forms? Right handed vs. left handed • Earlobes: Two forms? • ` Attached vs. unattached • Curliness of hair: Two forms? Curly vs. straight • Freckles: Two forms? Freckles vs. no freckles • Dimples: Two Forms? Dimples vs. no dimples • Cleft Chin: Two Forms? Cleft chin vs. no cleft chin

  8. How do we inherit either form of one of these traits? • KP#1: There are two types of genes: dominant (CAPITAL LETTER) and recessive (lowercase letter). This guy represents a dominant gene. Dominant means strong This guy represents a recessive gene. recessive means weak

  9. LETS PRACTICE! Is it a Dominant or a Recessive Gene? f b RECESSIVE RECESSIVE g T DOMINANT RECESSIVE r L RECESSIVE DOMINANT

  10. Our two genes combine to make a trait: • AA = two dominant genes = shows dominant trait • aa = two recessive genes = shows recessive trait • Aa = one dominant and one recessive gene What do you think will show? DOMINANT! DOMINANT BEATS RECESSIVE Which guy do you think represents the dominant gene and which guy represents the recessive gene?

  11. WHAT’S THE RULE?? KP #2: A dominant trait will show if you have ONE or TWO dominant genes.  AA or Aa KP #3: A recessive trait will show ONLY if you have TWO recessive genes.  aa

  12. LETS PRACTICE! Will these gene combinations show a Dominant or a Recessive Trait? Ff bb RECESSIVE DOMINANT TT Gg DOMINANT DOMINANT rr LL RECESSIVE DOMINANT

  13. Who’s tired of saying GENE COMBINATION? KP# 4: Another word for gene combinations is GENOTYPE. (THINK GENE) EX: Aa = genotype Another word for trait or the way an organism looks or behaves is PHENOTYPE. (THINK PHYSICAL) Ex: Curly hair = phenotype

  14. LETS PRACTICE! Genotype or Phenotype? Straight hair line: Jj: Genotype Phenotype Cc: Freckles: Genotype Phenotype Tt: Genotype Dimples: Phenotype

  15. What about wavy hair? What gene combination do you think creates wavy hair? -Aa KP #5: Sometimes the dominant gene does not completely overpower the recessive gene. This is called incomplete dominance.

  16. CANDY QUESTION: Could it be possible for this little girl to have her own daughter some day with straight hair?

  17. YES! HOW? If the curly haired girl has a genotype that shows INCOMPLETE DOMINANCE, she still has an allele for straight hair. She could pass that on to her own child. What genotype MUST this little girl have? aa = straight hair aa = straight hair or Aa = wavy hair What genotype must this girl’s MOTHER have?

  18. YOUR TURN TO SHOW WHAT YOU LEARNED! START YOUR INDEPENDENT PRACTICE NOW.

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