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Extensions to Mendel Group Assessment

Palamino Horses – Incomplete Dominance

1. In horses there are two alleles for coat color: B – brown and b- for white. A horse that is BB is brown, a horse that is bb is white and a horse that is Bb is Palamino (golden in color with a blonde tail and mane). This trait is said to show incomplete dominance. Why?

2. If a brown horse and a white horse were mated what would you predict their fowl would look like? (show your work)

3. Two horses were mated and they produced four children: 1 was brown, 2 were palamino, and 1 was white. What are the genotypes of the two parents?

• Parent #1

• Parent #2

4. Why do we consider this an extension of what Mendel originally discovered?

Spotted Horses - Codominance

5. It was observed that when a black horse is cross with a white horse the offspring are spotted. Using a punnett square determine the phenotypic and genotypic ratios of the following cross:

Black horse (BB) x Spotted horse (BW)

6. What is the difference between incomplete dominance and codominance?

Blood-Typing – Multiple Alleles

Everyone knows that there are four main blood types: A, B, AB, and O. Carbohydrates on the surface of red blood cells cause the different types of blood. The gene responsible for producing these cell-surface carbohydrates is called I. This gene has three alleles: IA, IB, and i. Of the alleles IA and IB are codominant, and both are dominant to i.

7. What is it called when there are more than 2 alleles for a gene?

8. COPY and complete the table below:

|Phenotype |Genotype (s) |

|A |IA IA or IA i |

|B | or |

|AB | |

|O |ii |

9. Using a Punnett Square, determine the genotype and phenotypes if a person with AB blood and a person with type O blood have children.

10. Several days after giving birth at a local hospital, Mrs. and Mr. Abaloney leave with their new baby daughter. Upon arriving at home Mrs. Abaloney is overcome by a strange feeling that the hospital has given her the wrong baby. She returns the next day and demands that blood tests be conducted. The doctor determines that Mrs. Abaloney’s blood type is AB, Mr. Abaloney’s blood type is B and the baby is O. You are the doctor assigned to analyze the results and come to some conclusion about this disturbing case. Is this really the Abaloney’s baby? Explain why you do or do not think so and use the Punnett square to support your reasoning.

Skin Color – Polygenic Traits

There are three known genes that contribute to skin color. Each gene shows incomplete dominance resulting in approximately seven different skin colors.

11. What is it called when two or more genes control a single characteristic? What is one example of this in humans?

Skin Color – Polygenic Traits

There are three known genes that contribute to skin color. Each gene shows incomplete dominance resulting in approximately seven different skin colors.

Use the pictures to the left to answer #12 and #13.

12. Looking at the P generation, is it possible for them to have a very light child? Explain?

13. Looking at the F1 generation, is it possible for them to have a very light child? Explain?

X-Linked Traits

Hemophilia is caused by a recessive allele on the X chromosome.

14. A woman who is heterozygous for hemophilia marries a normal man. What are the phenotypes of their children? Calculate the probability.

15. A hemophiliac woman has a phenotypically normal mother. What are the genotypes of her mother and father?

Colorblindness is caused by a recessive allele on the X chromosome.

16. What is the probability that a color-blind woman who marries a man with normal vision will have a color-blind child?

17. Why are problems 14-16 often referred to as 'sex-linked' or ‘x-linked’ genetics problems?

Indicate whether your group believes each statement is true or false. IF false, re-write as a true statement.

18. ________ In any population of organisms the dominant allele for a trait will always be more common than the recessive allele.

19. ________ If you resemble one parent more than the other, you probably inherited more of your genes from that parent.

20. ________ The father determines the sex of a child.

21. ________ A woman with A type blood can only have a baby with A type blood.

22. ________ Hemophilia, an X linked disease occurs more often in males than in females.

23. ________ Polygenic traits normally have two different phenotypes.

24. ________An offspring of a chicken with black feathers and a chicken with white feathers is a chicken with both black and white feathers, is an example of codominance.

25. ________ The coat of the common house mouse comes in three different varieties brown, white and grey. Inheritance patterns of this trait could probably be explained by using complete dominance.

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