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EXPERIMENT 1: PUNNETT SQUARE CROSSES Part 1: Post-Lab Questions 1. Set up and complete Punnett squares for these crosses (remember Y = yellow, y = blue): a. YY and Yy b. YY and yy 2. Answer these questions: a. What are the resulting phenotypes? b. Are there any blue kernels? c. How can you tell whether or not there are blue kernels? 3. Set up and complete a Punnett square for a cross of two of the F1 from Step 1 (above). 4. Answer these questions: a. What are the genotypes of the F2 generation? b. What are their phenotypes? c. Are there more or fewer blue kernels than in the F1 generation? 5. Identify the four possible gametes produced by the following individuals (S = smooth, s = wrinkled): a. YY Ss: b. Yy Ss:

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2. Answer: a. Resulting phenotypes: 100% Yellow.

                   b. No, there are not blue kernels.

                   c. All kernels are yellow because the yellow allele (Y) is    

                       dominant  over blue allele (y).

Explanation: Crosses a (YY x Yy) and b (YY x yy) result in yellow offspring with genotypes: 1) Dominant homozygote (YY) and 2) Heterozygous (Yy).

4. Answer: a. Genotypes: YY (25%) , Yy (50%) and yy (25%).

                  b. Phenotypes: Yellow  (75%) and blue (25%).

                  c. There are more blue kernels in the F2 than in the F1.

Explanation: Crosses between F1 members (Yy x Yy)  result in yellow and blue offspring with genotypes: 1) Dominant homozygote (YY, 25%)  2) Heterozygous (Yy, 50%) and 3) Recessive homozygote (yy, 25%).

5. Answer: a. Ys and YS

                   b. YS, yS, Ys, ys.

Explanation: The yellow and smooth individuals with genotype  (YYSs) can produce two different gametes: Ys (Yellow and wrinkled) and YS (Yellow and smooth). The yellow and smooth individuals with genotype  (YySs) can produce four different gametes: YS (yellow ans smooth), yS (Blue and smooth), Ys (Yellow and wrinkled) and ys (Blue and wrinkled).

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2)a. 100% yellow / b. No, 0% blue kernels / c. assuming complete dominance only the genotype yy expresses blue kernels. 4)a. 1/4 = 25% YY, 1/2 = 50% Yy, 1/4 = 25% yy / b. 3/4 = 75% yellow, 1/4 = 25% blue / c. More. 5)a. YS, Ys, YS, Ys / b. YS, Ys, yS, ys

What is a Punnett square?

The Punnett square is a graphic representation that shows the different types of gamete combinations according to the alleles involved in a cross.

Punnett square shows the probabilities of getting offspring with different genotypes and their consequent phenotypes.

1) In the problem,

  • Y allele is dominant and expresses Yellow
  • y allele is recessive and expresses blue

a) Cross:

Parentals) YY  x  Yy

Gametes) Y   Y   Y   y

Punnett square)   Y     Y

                     Y    YY    YY

                      y    Yy     Yy

F1) 1/2 = 50% of the progeny will be h0m0zyg0us dominant, YY

     1/2 = 50% of the progeny will be heter0zyg0us, Yy

     100% of the progeny will be yellow

b. Cross:

Parentals) YY  x  yy

Gametes) Y   Y   y   y

Punnett square)   Y     Y

                      y    Yy    Yy

                      y    Yy     Yy

F1) 100% of the progeny will be heter0zyg0us, Yy

     100% of the progeny will be yellow

2) Answer these questions:

a. What are the resulting phenotypes?

The whole progeny in both crosses will be yellow.

b. Are there any blue kernels?

No, there are no blue kernels among the progeny.

c. How can you tell whether or not there are blue kernels?

Assuming complete dominance, blue kernels are expressed by the genotype yy, h0m0zyg0us recessive.

Since the F1 of both crosses carry the dominant allele Y, we expect to see all yellow kernels.

3) Between two heter0zyg0us individuals

Parentals)  Yy   x   Yy

Gametes) Y   y    Y   y

Punnett square)  Y      y

                       Y   YY    Yy

                        y   Yy     yy

F2)

1/4 = 25% of the progeny is expected to be h0m0zyg0us dominant, YY

1/2 = 50% of the progeny is expected to be heter0zyg0us Yy

1/4 = 25% of the progeny is expected to be h0m0zyg0us recessive, yy

3/4 = 75% of the progeny is expected to be yellow

1/4 = 25% of the progeny is expected to be blue

4)

a)  Genotypes of the F2 generation

  • 1/4 = 25% YY
  • 1/2 = 50% Yy
  • 1/4 = 25% yy

b) Phenotype

  • 3/4 = 75% yellow
  • 1/4 = 25% blue

c) There are more blue kernels than in the F1 generation. The recessive phenotype appeared.

5)

  Genotype     Gametes

a.      YY Ss  ⇒ YS, Ys, YS, Ys

b.       Yy Ss  ⇒  YS, Ys, yS, ys

You will learn more about punnett square at

https://brainly.com/question/25357981

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