Chapter 9Chapter 9GeneticsGenetics

Why…Why…

• When 2 giraffes mate, do you only get another giraffe?

• …. Why don’t you get a porcupine instead?

How come we look like How come we look like • Our parents and brothers and

sisters?

Heredity= passing traits to Heredity= passing traits to offspringoffspring

• Traits= eye-color, hair-color, height, skin color, personality, diseases, etc.

• Offspring= what’s born, puppies, babies, kittens

• Genotype: what your DNA code says• Phenotype: what shows on the

outside

AllelesAlleles• We use letters to represent traits

when we study genetics. • ½ chromosomes come from dad and

½ come from mom ….so 2 letters for every trait

• Ex: eye color= letter b • B= brown b= blue

Dominant/ RecessiveDominant/ Recessive• So the different combinations of

those letters are…• BB: genotype (carries 2 brown),

phenotype (shows brown)• Bb: genotype (carries both),

phenotype (shows brown)• bb: genotype (carries only blue),

phenotype (shows blue)

• So brown eyes were dominant …

Figure 1: Forty shades of color.

Incomplete DominanceIncomplete Dominance• White + red= ______________• Curly + straight= ________________

• CC

• Cc

• cc

Co- dominanceCo- dominance• CC• Cc• cc• What do you think this means….

Co- dominanceCo- dominance• RR- brown• Rr- white with brown spots• rr- white• Both traits are expressed at the

same time