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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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marianaegarciaperedo

Punnett squares are used to get the genotypic and phenotypic frequencies among the progeny produced from a cross. Punnett squares and answers below.

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.

In the exposed example,

  • Diallelic genes that codes for color
  • Y = yellow ⇒ dominant allele
  • y = blue ⇒ recessive allele

We will assume complete dominance, meaning that with at least one dominant allele in the genotype, the expressed color is yellow.

1)

a- Cross 1

Parentals)   YY   x    Yy

Gametes) Y   Y      Y   y

Punnett square)      Y        Y

                        Y     YY      YY

                         y     Yy      Yy

F1) Genotype

1/2 = 50% of the progeny is expected to be homozygous dominant, YY

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

   

    Phenotype

100% of the progeny is expected to be yellow.

b- Cross 2

Parentals)  YY   x    yy

Gametes) Y     Y     y    y

Punnett square)      Y        Y

                        y     Yy     Yy

                         y    Yy      Yy

F1) Genotype

100% of the progeny is expected to be heterozygous, Yy

   

    Phenotype

100% of the progeny is expected to be yellow.

2)

a. What are the resulting phenotypes? Only yellow kernels

b. Are there any blue kernels? No

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

Blue is the recessive phenotype for kernels. Assuming complete dominance, since all genotypes are expected to carry at least one dominant allele, all the F1 kernels are yellow.  

3) Let us cross two heterozygous individuals from the F1

Parentals)  Yy   x    Yy

Gametes) Y    y     Y    y

Punnett square)     Y        y

                        Y    YY     Yy

                         y    Yy      yy

F1) Genotype

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

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

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

    Phenotype

75% of the progeny is expected to be yellow.

25% of the progeny is expected to be blue.

4)

a. What are the genotypes of the F2 generation?

- 25% YY (homozygous dominant)

- 50% Yy (Heterozygous)

- 25% yy (Homozygous recessive)

b. What are their phenotypes?

- 75% yellow kernels

- 25% blue kernels

c. Are there more or fewer blue kernels than in the F1 generation?

More. Blue kernels appeared in the F2.

5. Assuming independent genes, the , are as follows

                         Gametes

a. YY Ss   ⇒   YS, YS, Ys, Ys

b. Yy Ss  ⇒     YS, Ys, yS, ys

You can learn more about punnett squares at

https://brainly.com/question/25357981

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