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Pedigree Worksheet 20 Points Name Period INTRODUCTION Pedigree charts are often constructed to show the inheritance of genetic conditions within a family. Such charts are a great help in determining whether a phenotype is controlled by a dominant, recessive or sex-linked allele. PART I - Understanding the Pedigree Male Female Affected individual Mating Offspring in birth order; I and II are generations; offspring numbered II-1 and II-2 Identical twins Non-identical twins The symbols of the pedigree are listed on the left. After analyzing the pedigrees, conclusions about the different modes of inheritance can be made. There are three types of inheritance for which pedigrees can be used: Autosomal Dominant: Each affected individual has an affected parent; there is no skipping of generations. Males and females are equally likely to be affected. Autosomal Recessive: An affected individual may not have an affected parent. (Both parents could be heterozygous) Males and females are equally likely to be affected. X-link Recessive: An affected individual may not have an affected parent. Males are more likely to be affected than females. Males also cannot be carriers of the recessive gene. (If they have the X-linked gene, they will show the trait) PART II – Pedigree Huntington’s Disease I 1 2 II 1 2 3 4 5 6 7 8 = Huntington's Disease III 1 2 3 4 5 1. There are no carriers for Huntington’s Disease- you either have it or you don’t. What type of complex inheritance is this? _ 2. With this in mind, is Huntington’s disease caused by a dominant or recessive trait? _ 3. Which members of the family above are afflicted with Huntington’s Disease? _ 4. How many children did individuals I-1 and I-2 have? _ 5. How many girls did II-1 and II-2 have? _ How many have Huntington’s Disease? _ 6. How is individual III-2 and II-4 related? _ I-2 and III-5? _

Pedigree Worksheet
20 Points
Name
Period

INTRODUCTION
Pedigree charts are often constructed to show the inheritance of genetic conditions within a family. Such charts are a great help in determining whether a phenotype is controlled by a dominant, recessive or sex-linked allele.

PART I - Understanding the Pedigree

Male
Female
Affected individual
Mating
Offspring in birth order; I and II are generations; offspring numbered II-1 and II-2
Identical twins
Non-identical twins

The symbols of the pedigree are listed on the left. After analyzing the pedigrees, conclusions about the different modes of inheritance can be made. There are three types of inheritance for which pedigrees can be used:

Autosomal Dominant: Each affected individual has an affected parent; there is no skipping of generations. Males and females are equally likely to be affected.

Autosomal Recessive: An affected individual may not have an affected parent. (Both parents could be heterozygous) Males and females are equally likely to be affected.

X-link Recessive: An affected individual may not have an affected parent. Males are more likely to be affected than females. Males also cannot be carriers of the recessive gene. (If they have the X-linked gene, they will show the trait)

PART II – Pedigree Huntington’s Disease

I
1
2

II
1
2
3
4
5
6
7
8

= Huntington's Disease

III
1
2
3
4
5

1. There are no carriers for Huntington’s Disease- you either have it or you don’t. What type of complex inheritance is this? ___

2. With this in mind, is Huntington’s disease caused by a dominant or recessive trait? ___

3. Which members of the family above are afflicted with Huntington’s Disease? ___

4. How many children did individuals I-1 and I-2 have? ___

5. How many girls did II-1 and II-2 have? ___ How many have Huntington’s Disease? ___

6. How is individual III-2 and II-4 related? ___ I-2 and III-5? ___

Pedigree Worksheet
20 Points
Name
Period

INTRODUCTION
Pedigree charts are often constructed to show the inheritance of genetic conditions within a family. Such charts are a great help in determining whether a phenotype is controlled by a dominant, recessive or sex-linked allele.

PART I - Understanding the Pedigree

Male
Female
Affected individual
Mating
Offspring in birth order; I and II are generations; offspring numbered II-1 and II-2
Identical twins
Non-identical twins

The symbols of the pedigree are listed on the left. After analyzing the pedigrees, conclusions about the different modes of inheritance can be made. There are three types of inheritance for which pedigrees can be used:

Autosomal Dominant: Each affected individual has an affected parent; there is no skipping of generations. Males and females are equally likely to be affected.

Autosomal Recessive: An affected individual may not have an affected parent. (Both parents could be heterozygous) Males and females are equally likely to be affected.

X-link Recessive: An affected individual may not have an affected parent. Males are more likely to be affected than females. Males also cannot be carriers of the recessive gene. (If they have the X-linked gene, they will show the trait)

PART II – Pedigree Huntington’s Disease

I
1
2

II
1
2
3
4
5
6
7
8

= Huntington's Disease

III
1
2
3
4
5

1. There are no carriers for Huntington’s Disease- you either have it or you don’t. What type of complex inheritance is this?

2. With this in mind, is Huntington’s disease caused by a dominant or recessive trait?

3. Which members of the family above are afflicted with Huntington’s Disease?

4. How many children did individuals I-1 and I-2 have?

5. How many girls did II-1 and II-2 have? How many have Huntington’s Disease?

6. How is individual III-2 and II-4 related? I-2 and III-5?

Added by Olga R.

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