Download Human Pedigree Genetics

Human Pedigree Genetics
Name __________________
Class _____ Date _________
Objective: At the end of this activity you should be able to analyze a family pedigree and use it to
determine the unknown genotypes of members of a family.
Procedure: Study each of the following families with certain hereditary traits. Determine whether
the gene for the trait listed is dominant or recessive and determine the genotype and phenotype of
each individual in the family. It may not be possible to determine the exact genotype of every
individual in the pedigree so simply put a question mark by those that are unknown. If you know
one of the alleles, record it and write a “?” in the place of the second allele. (ie: D?). Record the
genotypes on this lab.
Data:
Pedigree Chart Symbols
Symbol
Meaning
Parents
1
Male
2
Female
Children
Af fected individual
1
2
3
4
5
6
Stillborn
Grandchildren
Fraternal twins
1
2
3
4
5
Pedigree A. Deaf Mutism
One form of deafness in humans is a type in which the individual inherits not only deafness but also the inability to talk.
Use symbols D for dominant, d for recessive.
Deaf Mutism
I
1
2
II
1
III
1
2
2
3
2
3
3
4
5
6
5
6
7
4
5
8
9
6
10
7
11
12
12
13
8
13
14
16
17
IV
1
4
7
8
9
10
1 1
14
15
18
Pedigree B. Hemophilia
Hemophilia is a disease of the circulatory system. It is sometimes called the bleeder’s disease because persons with the
disease have a very long clotting time when injured. An affected person could bleed to death from minor wounds or
internal injuries. Hemophilia is a sex-linked trait. Use the symbols XH for dominant, Xh for recessive.
Hemophilia
I
1
2
II
1
2
3
4
5
6
7
8
9
16
17
III
1
2
3
4
5
6
5
6
7
8
9
10
1
1
12
13
14
15
18
IV
1
2
3
4
7
8
Pedigree C. Brachydactyly
Brachydactyly is a condition in which fingers are abnormally short. Use symbols B for dominant, b for recessive.
Caution: Before you begin determine if brachydactyly is a dominant or a recessive trait.
Brachydactyly
I
II
1
1
III
2
1
3
2
3
4
4
5
5
2
6
7
8
9
6
7
8
9
10
11
4
5
6
7
8
9
10
12
13
14
IV
1
2
Human Pedigree Genetics
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10
2
Conclusion:
1. In pedigree A, why do parents 13 and 14 in generation III have all deaf children?
2. In pedigree A, how can parents 1 and 2 of generation I, have a deaf child even though neither parent is deaf?
3. In pedigree A, why don’t parents 8 & 9 and 11 & 12, in generation III, have at least one deaf child.
4. List by number the persons in pedigree A for which you cannot determine a genotype. For example: II-1.
5. Why can’t you determine the genotypes of these people?
6. In pedigree B, how can unaffected parents have an affected child?
7. What is the genotype of the mothers of all affected females in pedigree B? Explain.
8. What characteristic do all of the affected females in pedigree B have in common?
9. Is the brachydactyly trait in pedigree C dominant or recessive? ________________ Explain.
Human Pedigree Genetics
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