BIO 112 Laboratory Report Sheet: Complex Inheritance and Stem Cells

13 Jun BIO 112 Laboratory Report Sheet: Complex Inheritance and Stem Cells

Question
Laboratory Report Sheet: Complex Inheritance and Stem Cells

Exercise 1: Pedigree of a Human Trait
The following diagram represents the pedigree of a family that shows the inheritance of a human disorder called PKU (phenylketonuria). This disorder is produced by a recessive allele. The dominant allele produces a normal individual. A person who is heterozygous for this trait is referred to as a carrier, although this person does not show the symptoms of PKU.

In the diagram below, a square indicates a male, while a circle is the symbol for a female. An unshaded symbol indicates a normal person and the dark symbol denotes a person afflicted with the disorder. The Roman numerals indicate the generations (I, II, III, IV), while Arabic numbers designate the individuals within each generation (1, 2, 3, etc.). A marriage of two individuals is indicated by a horizontal line connecting their symbols. A marriage between blood relatives (consanguinity) is shown by two horizontal lines. Study the family pedigree, and answer the questions below.

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What is the phenotype and genotype of individual 7 in generation II? (1 point)
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What is the phenotype and genotype of individuals 1 and 2 in generation I? (1 point)
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Can you say with certainty what the genotypes of individuals 1-5 in generation II might be? Why? (1 point)
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The children of II6 and II7 indicate that II6 has what genotype? (1 point)
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The marriage and offspring of cousins III8 and III9 reveals that III8 has what genotype? (1 point)
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Individuals III3 and III4 have what genotype? (hint: look at their children IV 1, 2, 3). (1 point)
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Exercise 2: Incomplete Dominance
In module 10, you studied traits that were produced by the complete dominance of one gene over another. However, there are a number of characteristics in humans and other organisms that do not exhibit this exact mode of inheritance. One alternate method is called incomplete dominance or intermediate inheritance. In this mode of inheritance, both of the alleles of a heterozygous individual express their phenotype, thus there is no clear dominance of one gene over another. The phenotype of a heterozygote is therefore intermediate between the phenotypes of the individuals homozygous for each allele.

Now consider the a few examples of incomplete dominance observed in humans. These are problems to be answered:

A. A gene produces very short fingers and toes (a condition called brachydactyly). Another allele of this gene produces normal length fingers and toes. The short finger-toe allele (Br) is incompletely dominant to the normal finger-toe allele (Br’). A homozygous Br individual has no fingers or toes, while the homozygous Br’ person has normal fingers and toes. The heterozygous individual has abnormally short fingers and toes.

1. If two short fingers individuals marry, how many of their children would be expected to have short fingers-toes? Enter Response(1 point)

2. How many of their children would have no fingers-toes? Enter Response(1 point)

3. What proportion of their children would have normal fingers-toes? Enter Response(1 point)

4. If a short finger man marries a female with normal fingers, what will their children be like as to length of their fingers-toes? Enter Response(1 point)

B. Another example of incomplete inheritance is the human trait for the type hemoglobin molecules found in red blood cells (RBC). One allele produces normal hemoglobin, and its symbol is HA. The other allele produces abnormal hemoglobin, and its symbol is HS. When this allele is present, it causes RBC to become sickle-shaped when there is insufficient oxygen present. The sickling of blood cells produces various symptoms of anemia and may be lethal. A homozygous HA individual has normal hemoglobin and has no problems of transporting oxygen. The homozygous HS individual suffers from sickle cell anemia in an oxygen-deficient condition. Under these same conditions, the heterozygous individual, HAHS, shows only a mild sickling of RBC and some discomfort. The heterozygous individual is said to have the sickle cell trait.

1. What are the chances that a sickle cell trait husband and a normal wife will have sickle cell trait children? Enter Response(1 point)

Remember that in cases of incomplete dominance, the heterozygous individual’s phenotype seems to be a blend of the two extremes.

Exercise 3: Co-Dominant Inheritance
Another variation of inheritance is one in which there are more than two alleles of a gene and two or more of the alleles are equal in dominance over all others in the series of alleles. This is referred to as co-dominance. An example of this in humans is the inheritance of the ABO blood group. The alleles in this series are symbolized as IA, IB, and i. The IA allele produces one type of protein (agglutinogen) on the surface of a RBC, while the IB allele produces a completely different protein on the cell’s surface. These two alleles are both dominant to the third allele i, which produces no surface proteins. If the two dominant alleles are present together, as in a heterozygous individual, both produce their protein (there is no “blending” as in intermediate inheritance) and therefore both alleles are said to be co-dominant.

The four human blood types of the ABO series are produced in the following way:

Type A has agglutinogen (protein) A, produced by allele IA.

Type B has agglutinogen (protein) B, produced by allele IB.

Type AB has both agglutinogens, produced by the presence both co-dominant alleles.

Type O has neither agglutinogens, due to the presence of the recessive allele i.

Complete the following chart: (4 points)

Phenotype

Possible Genotype(s)

A

Enter Response

B

Enter Response

AB

Enter Response

O

Enter Response

1. What blood types will the children of a type O mother and father have?(1 point)

Enter Response

2. What blood types will the children have whose parents are both type AB?(1 point)

Enter Response

3. What blood types will the children have if their mother is heterozygous type A and their father is heterozygous type B?( 1 point)

Enter Response

Exercise 4: Sex-linked Inheritance
The various types of inheritance that we have studied in module 10 and the previous parts of this lab unit have been due to genes that are located on the autosomes. Another type of inheritance involves genes located on the sex chromosomes. These genes are referred to as sex-linked genes. Genes that are carried on the X-chromosome are referred to as being X-linked. Since the human male (XY) has only on X-chromosome, any gene on that chromosome will be expressed in the phenotype, regardless of whether it is dominant or recessive. The male can never be heterozygous for a sex-linked gene, since he has only the one X-chromosome. In the human female (XX), a recessive gene on the X-chromosome must be homozygous before it is expressed in the phenotype. In sex-linked inheritance, males cannot pass their X-chromosome genes to their sons, because the male can pass only the Y-chromosome to his son and his X-chromosome to his daughter.

An interesting X-linked trait is the bleeder’s disease or hemophilia, when the blood does not clot properly due to the absence in the blood of one of the essential factors required in the blood clotting reaction. A hemophiliac person bruises easily and tends to bleed profusely from even minor scratches. This trait is due to a recessive allele.

How could a female be a hemophiliac if her mother is a non-bleeder?(1 point)
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What kind of children could a couple expect if the mother is a carrier of hemophilia, and the father has normal blood clotting?( 1 point)
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Review Questions
Describe how chromosomes determine the sex of a child.(1 point)
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Describe how X-linked traits are inherited.(1 point)
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Contrast stem cells and fully differentiated cells.(2 points)
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Differentiate between embryonic and adult stem cells.(2 points)
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What are some of potential benefits of using stems in regenerative medicine?(2 points)
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Normal color vision in the human is due to a dominant gene, C, and is x-linked. The recessive form of the gene, c, causes the individual to be red-green color blind. A color blind woman marries a man with normal color vision. What are the possible phenotypes of children with respect to vision?(1 point)
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Shannon, a famous reality TV starlet, claims that Jocko Johnson, star quarterback of the Ocelots, is the father of her baby Cornelius. This is a fact that Jocko strongly denies. Shannon has type A blood, while her baby Cornelius has type O, and Jocko has type AB. Could Jocko possibly be the father? Why or Why not? (1 point)
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In humans, normal skin pigmentation is due to a dominant allele (A), while the recessive allele (a) causes albinism (lack of pigment in the skin, hair and eyes). Kendal is a normally pigmented woman who has a father that is albino. She marries Kent, an albino man. Complete the Punnett square to answer the following questions: (4 points)What is Kent’s genotype?

Aa and aa

What is Kendal’s genotype?
Aa

Sperm

Eggs

Aa

Aa

aa

Aa

List all the possible phenotypes and genotypes of the children that this couple may have?
Enter Response

What is the chance this couple would have a child with normal skin pigmentation.
Enter Response