Course Bio 101
anwsers
BIO 101 Punnett Squares
http://www.mhhe.com/biosci/genbio/virtual_labs_2K8/labs/BL_05/index.htmlRead 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.