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Course  Bio 101    
anwsers

BIO 101    Punnett Squares

http://www.mhhe.com/biosci/genbio/virtual_labs_2K8/labs/BL_05/index.html

Read through the instructions on the right.  Watch the video on the “TV” to learn about how to set up a Punnett square.  Then, when ready, click the lab notebook to begin working the problems.

A scenario will be shown in the upper left-hand corner.  To set up the parents, click and hold the “down triangle” below each parent.  Then choose the parent fly that you want.  After you have set up both parents click “Check Parents”.  Once the parents are correct, click and drag the genotypes and phenotypes of the offspring into the boxes in the Punnett square.  Click “Check Offspring” when you have the Punnett square completed.  Once you have completed it successfully, click “Reset” to get another scenario. 

The scenarios are given at random.  Please make sure to look at the number so that you are filling out the correct part on this worksheet!  If you get a scenario you have already done, click “Reset” to get another scenario.  (Scenario #1 has been done for you to show you how to answer the others.)

Scenario #1

Parent 1         Parent 2   
Genotype (alleles)    Gg      Genotype (alleles)    gg
Genotype (term)   Heterozygous      Genotype (term)   Homozyous recessive
Phenotype   Grey body      Phenotype   Black body

Expected genotype ratio of the offspring:
   1 Gg: 1 gg (or 2 Gg: 2 gg)

Expected phenotype ratio of the offspring:
   1 black: 1 grey (or 2 black: 2 grey)

   


Scenario #2

Parent 1         Parent 2   
Genotype (alleles)    Gg      Genotype (alleles)    Gg
Genotype (term)   Heterozygous      Genotype (term)   Heterozygous
Phenotype   Grey Body      Phenotype   Grey Body

Expected genotype ratio of the offspring:
   1: GG; 2: Gg; 1: gg


Expected phenotype ratio of the offspring:
   Three grey body, one black body.



Scenario #3

Parent 1         Parent 2   
Genotype (alleles)    LL      Genotype (alleles)    ll
Genotype (term)   Homozygous      Genotype (term)   Homozygous
Phenotype   Long winged      Phenotype   Vestigial winged

Expected genotype ratio of the offspring:
   Ll:4

Expected phenotype ratio of the offspring:
   Long winged







Scenario #4

Parent 1         Parent 2   
Genotype (alleles)    LL      Genotype (alleles)    Ll
Genotype (term)   Homozygous      Genotype (term)   Heterozygous
Phenotype   Long- winged      Phenotype   Long-Winged

Expected genotype ratio of the offspring:
   LL: 2; Ll: 2

Expected phenotype ratio of the offspring:
   4: Long-winged






Scenario #5

Parent 1         Parent 2   
Genotype (alleles)    Ll      Genotype (alleles)    Ll
Genotype (term)   Heterozygous      Genotype (term)   Heterozygous
Phenotype   Long winged      Phenotype   Long winged

Expected genotype ratio of the offspring:
   LL;1 Ll;2 ll;1

Expected phenotype ratio of the offspring:
   3 long winged 1 vestigial winged






Scenario #6

Parent 1         Parent 2   
Genotype (alleles)    GG      Genotype (alleles)    Gg
Genotype (term)   Homozygous      Genotype (term)   Heterozygous
Phenotype   Grey  body      Phenotype   Grey body

Expected genotype ratio of the offspring:
   GG;2   Gg;2

Expected phenotype ratio of the offspring:
   Grey body






Scenario #7

Parent 1         Parent 2   
Genotype (alleles)    LL      Genotype (alleles)    ll
Genotype (term)   Homogenous      Genotype (term)   Homogenous
Phenotype   Long-winged       Phenotype   Vestigial-Winged

Expected genotype ratio of the offspring:
   Ll: 2; ll: 2
Expected phenotype ratio of the offspring:
   Long-winged: 2; Vestigial-Winged: 2






Scenario #8

Parent 1         Parent 2   
Genotype (alleles)    GG      Genotype (alleles)    gg
Genotype (term)   Homozygous      Genotype (term)   Homozygous
Phenotype   Grey-Bodied      Phenotype   Black-bodied

Expected genotype ratio of the offspring:
   Gg: 4

Expected phenotype ratio of the offspring:
   4: grey-bodied





Scenario #9

Parent 1         Parent 2   
Genotype (alleles)    ll      Genotype (alleles)    ll
Genotype (term)   Homozygous      Genotype (term)   Homozygous
Phenotype   Vestigial wing      Phenotype   Vestigial winged

Expected genotype ratio of the offspring:
   ll: 4

Expected phenotype ratio of the offspring:
   
4; vestigial






Scenario #10

Parent 1         Parent 2   
Genotype (alleles)    gg      Genotype (alleles)    gg
Genotype (term)   Homogenous      Genotype (term)   Homogenous
Phenotype   Black Body      Phenotype   Black Body

Expected genotype ratio of the offspring:
   4: gg

Expected phenotype ratio of the offspring:
   4 Black Body




 Summary Questions

1) If you are given a grey-bodied fly, do you know the genotype of it?  Why or why not?

I do not know, because it can be Homogenous or Heterozygous

2) You are given a long-winged fly and told to determine its genotype.  What cross would you perform?  Explain how the results would tell you the genotype of this long-winged fly.

If I was given a Long-winged fly, the way I would determine its genotype is by crossing two homozygous long wing- flies or two heterozygous long-wing fly or a homozygous long-winged fly with a homozygous vestigial wing-fly


3) Explain why an organism that is homozygous dominant has the same phenotype as an organism that is heterozygous.
Because, it has one dominate allele and one recessive allele.


4) What information can you get from a Punnett square?  What information can you NOT get from a Punnett square?

What you can get from a Punnett square is you can know all the possible gene expressions.

What I cannot get from a Punnett square is,  you know which of the four options are going to be the end results.
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