Complete Dominance

1. Complete Dominance • One parent is heterozygous for a trait. The other is homozygous. What fraction of their offspring will be heterozygous?

2. Pea plants having wrinkled seeds are crossed with pea plants having round seeds. Round is the dominant allele and the plant with round seeds is homozygous.

3. A sunflower with a long stem is crossed with a sunflower with a short stem. The plant with the long stem is heterozygous and the plant with the short stem is homozygous.

4. A mother and a father, both having brown eyes, have offspring with blue eyes. Show how this is possible using Punnett square and ratios.

5. Two black mice when mated produce some offsrping that are white. Explain with Punnett square and ratios.

6. You learned how Mendel crossed two plants of the F1 generation to test flower color. Pretend that you are Mendel crossing two plants of the F1 generation for seed color. Use your notes and your text to do the Punnett square and ratios for this trait. • If you produced 8023 plants, approximately how many plants will have yellow seeds and how many would have green seeds?

7. A heterozygous black guinea pig is mated with a homozygous recessive white guinea pig. Determine the gametes formed by each parent and work a Punnett square to predict the genotype and phenotype ratios of the offspring.

8. Pictured above is an alien who displays all of the dominant characteristics of its species.  I have given you a chart listing various traits found in this alien race.  Use the information in the chart to solve the genetics problems that follow.

9. A heterozygous male mates with a pure yellow female.  What is the chance this couple will produce an orange baby?  Check your answer

10. Two purple-eyed aliens mate.  Both aliens are hybrid for the eye color trait.  What is the chance this couple will produce a baby with a homozygous recessive genotype?  Check your answer

11. A heterozygous female with 3 body rings mates with a 5-ringed male.  What is the chance that this couple will have a baby that looks like its mother?   Check your answer

12. A pure male alien displaying the dominant body color mates with a female that is homozygous recessive for this characteristic.  What is the chance that this couple will have a baby with a hybrid genotype?  Check your answer

13. A male alien with 1 antenna mates with a female alien who has 2 antennae.  The female is heterozygous for the antenna trait.  What is the chance that this couple will produce a baby with the recessive phenotype?  Check your answer

14. An alien couple, both of which wear glasses, are having a baby.  The male's genotype is heterozygous.  The female is phenotypically dominant but does carry the recessive allele.  What is the chance that this couple's baby will have to wear glasses?  Check your answer

15. A 3-ringed female mates with a homozygous male.  The female has been genetically tested and is carrying both the dominant and the recessive allele for this trait.  The male displays the recessive phenotype.  What is the chance that this couple will have a genetically pure baby? Check your answer

16. Dihybrid Crosses • Two traits for guinea pigs are coat texture (rough or smooth) and coat color (black or albino). R=rough; r=smooth; B=black; b=albino. A heterozygous black/ smooth coated male is bred with a heterozygous black/ heterozygous rough coated female. Use a Punnett square to solve for phenotype ratios.

17. Two parent pea plants that are heterozygous for flower color and heterozygous for pod shape are crossed. Determine the phenotype ratio for this cross.

18. The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume that red stripes are expressed from the homozygous RR genotype, yellow stripes from the homozygous rr genotype, and both from the heterozygous genotype. What will be the phenotypic ratio of the F1 generation resulting from a cross of two grasshoppers, both with red and yellow stripes (red : both : yellow)?

19. In Mendel's experiments, if the gene for tall (T) plants was incompletely dominant over the gene for short (t) plants, what would be the result of crossing two Tt plants?

20. Labrador retrievers demonstrate incomplete dominance for fur color. Black is incompletely dominant over yellow. If you cross to brown labs what are your chances of producing black labs?

21. One parent has type AB blood. The other parents has type B blood but is heterozygous. Determine ratios for blood type in offspring.

22. What are the chances of two human parents having a boy? Determine ratios to prove your answer.