Question

gummy bear genetics: patterns of inheritance
sb3.a use mendels laws (segregation and independent assortment) to ask questions and define problems that explain the role of meiosis in reproductive variability.
background
in sexual reproduction, ½ of an offsprings genes come from each parent. sexually produced offspring are not identical to their parents. dominant and recessive alleles control some traits. some traits are controlled by incomplete dominance. the chances of traits being expressed in offspring can be determined using punnett squares. gummy bears are popular attractions at the local zoo because of their bright colors and playfulness. one evening, the zookeepers found that all of the baby gummy bears from five (5) different families had escaped their habitat! not only were the babies loose, but the parents had also escaped in search of their cubs. while wandering through the zoo, sibling bears stayed together and were captured by the zookeeper (they were napping in the gift shop). it is your job to match the bear cubs with their parents based on the known patterns of skin color inheritance of this bear species. each family has four (4) cubs.
patterns of inheritance:
skin color in gummy bears follows several inheritance patterns with four possible alleles:
+simple dominance:
dominant: blue (b)
recessive: light blue (b)
+incomplete dominance
blue (b) + yellow (y)= green (by)
blue (b)+ red (r)= purple(br)
red (r ) + yellow (y)=orange (ry)
+codominance dominant:
green (g) + purple (p)= green and purple stripes (gp)
materials:

• gummy bear genetics handout, (1) 11 x 14 sheet of paper, glue, scissors
• paper gummy bears

instructions: write the correct genotype(s) for each of the following phenotypes:
phenotype genotype(s): some will have homozygous and heterozygous allele arrangements
blue
light blue
red
yellow
orange
green
purple
green and purple stripes

Explanation:

Step1: Identify dominant and recessive alleles for blue

Blue (B) is dominant and light - blue (b) is recessive. A blue gummy bear can have either a homozygous dominant (BB) or heterozygous (Bb) genotype.
BB, Bb

Step2: Determine genotype for light - blue

Since light - blue (b) is recessive, a light - blue gummy bear must have a homozygous recessive genotype.
bb

Step3: Assume red allele is R

Since no information about dominance for red other than in combination with other colors, assume a red gummy bear has a homozygous genotype RR.
RR

Step4: Assume yellow allele is Y

Similarly, assume a yellow gummy bear has a homozygous genotype YY.
YY

Step5: Analyze orange which is from red + yellow

Orange (RY) is a result of incomplete dominance between red (R) and yellow (Y), so the genotype is RY.
RY

Step6: Analyze green which is from blue + yellow

Green (BY) is a result of incomplete dominance between blue (B) and yellow (Y), so the genotype is BY.
BY

Step7: Analyze purple which is from blue + red

Purple (BR) is a result of incomplete dominance between blue (B) and red (R), so the genotype is BR.
BR

Step8: Analyze green and purple stripes

Green and purple stripes (GP) is a result of codominance between green (G) and purple (P), so the genotype is GP.
GP

Answer:

Blue: BB, Bb
Light Blue: bb
Red: RR
Yellow: YY
Orange: RY
Green: BY
Purple: BR
Green and Purple Stripes: GP