Name ________________________

Date _________________________

Genetics Worksheet

 

The Punnett Square:

The Punnett square is a chart, used by geneticists, to help determine the chances of an offspring receiving a particular characteristic. The Punnett square will not tell you how many offspring will develop, or the order in which they will be born. B = brown hair and b = blonde hair.

Example: --------------------------Bb X Bb ----------Parents that are heterozygous for Brown hair.

Gametes: ------------------------B and b ; B and b-------Each parent produces 2 gametes.

 

Punnett Square:

Gametes -------|---->	B	b
B	---------------------------------	----------------------
b	----------------------	---------------------

 

1. What are the chances of the offspring being homozygous brown haired? ____________.

2. What are the chances of the offspring having blonde hair? __________________.

3. What are the chances of the offspring being heterozygous brown haired? ___________.

4. What is the genotypic ratio? _________________.

5. What is the phenotypic ratio? ________________.

6. What is the dominant gene? _________________.

7. Is there a heterozygous blonde haired offspring? ___________. Why? ______________

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Questions:

8. If curly hair is dominant to straight hair, what letters will we use to show these genes?

9. If a heterozygous curly haired male marries a straight haired female, what would there genotypes look like using the letters in question 8 ? ________________X _________________.

10. What would be the gametes for the male parent? ____________________

11. What would be the gametes for the female parent? ___________________

12. Work out the Punnett square in the space below and answer the following questions.

 

Gametes -------|---->	B	b
B	---------------------------------	----------------------
b	----------------------	---------------------

 

13. What are the chances of the offspring being homozygous curly haired? ___________________.

14. What are the chances of the offspring having straight hair? __________________.

15. What are the chances of the offspring being heterozygous curly haired? ____________.

16. What is the genotypic ratio? _________________.

17. What is the phenotypic ratio? ________________.

18. What is the dominant gene? _________________.

19. Is there a heterozygous straight haired offspring? ___________. Why?____________

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20. If yellow pods are dominant to green pods, what letters will we use to show these genes?

21. If a heterozygous yellow male is crossed with another heterozygous yellow female, what would there genotypes look like using the letters in question 20 ? ________________X _________________.

22. What would be the gametes for the male parent? ____________________

23. What would be the gametes for the female parent? ___________________

24. Work out the Punnett square in the space below and answer the following questions.

 

Gametes -------|---->	B	b
B	--------------------------------	----------------------
b	----------------------	---------------------

 

25. What are the chances of the offspring being homozygous green? ________________.

26. What are the chances of the offspring being yellow? __________________.

27. What are the chances of the offspring being heterozygous yellow? ________________.

28. What is the genotypic ratio? _________________.

29. What is the phenotypic ratio? ________________.

30. What is the dominant gene? _________________.

31. Is there a heterozygous green offspring? ___________. Why? __________________

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