1. Chris and Emma are phenotypically normal but carriers for SCA (gene A). a. What are their genotypes? b. With respect to gene A, what are the possible genotypes of the gametes that they can produce. Emma: Chris: ||

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Chapter11: Genome Alterations: Mutation And Epigenetics
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The gene involved in the disease Sickle Cell Anemia (SCA) is on human chromosome 11. Allele
"A" is the normal form of the gene and codes for a part of the protein complex called hemoglobin.
Hemoglobin is required for your blood cells to carry oxygen. Allele "a" is an abnormal form of the gene.
The hemoglobin protein made from the "a" allele is defective. Red blood cells containing the defective
protein are very fragile. This disease is recessive-meaning that you have to inherit two copies of the
recessive allele in order to be affected with the disease SCA.
The gene involved in the disease Cystic Fibrosis (CF) is on human chromosome 7. Allele "B" is
the normal form of the gene and codes for a channel protein that allows chloride to pass through a cell.
Allele "b" is the abnormal form of the gene. The channel protein made from the "b" allele is defective and
doesn't insert into the cell's plasma membrane, resulting in an inability of sodium and chloride to cross the
membrane. CF is also recessive therefore only people with two defective copies of the gene ("bb") are
affected with the disease.
1. Chris and Emma are phenotypically normal but carriers for SCA (gene A).
a. What are their genotypes?
b. With respect to gene A, what are the possible genotypes of the gametes that they can produce.
Emma:
Chris:
In front of each gamete genotype above write probability of producing that gamete.
c. What is the probability that Chris and Emma will have a child affected with SCA?
(affected=has the disease="aa" =homozygous recessive)
d. Write the cross and the Punnett square that demonstrates this.
e. The phenotypic ratio is
The genotypic ratio is
normal :
affected
AA:
Aa :
aa
2. Chris and Emma are also carriers for CF (gene B is on chromosome 7). Both are genotype Bb.
a. What is the probability that they will have a child affected with CF?
(affected = has the disease = "bb" =homozygous recessive)
b. Write the cross and the Punnett square that demonstrates this.
Transcribed Image Text:The gene involved in the disease Sickle Cell Anemia (SCA) is on human chromosome 11. Allele "A" is the normal form of the gene and codes for a part of the protein complex called hemoglobin. Hemoglobin is required for your blood cells to carry oxygen. Allele "a" is an abnormal form of the gene. The hemoglobin protein made from the "a" allele is defective. Red blood cells containing the defective protein are very fragile. This disease is recessive-meaning that you have to inherit two copies of the recessive allele in order to be affected with the disease SCA. The gene involved in the disease Cystic Fibrosis (CF) is on human chromosome 7. Allele "B" is the normal form of the gene and codes for a channel protein that allows chloride to pass through a cell. Allele "b" is the abnormal form of the gene. The channel protein made from the "b" allele is defective and doesn't insert into the cell's plasma membrane, resulting in an inability of sodium and chloride to cross the membrane. CF is also recessive therefore only people with two defective copies of the gene ("bb") are affected with the disease. 1. Chris and Emma are phenotypically normal but carriers for SCA (gene A). a. What are their genotypes? b. With respect to gene A, what are the possible genotypes of the gametes that they can produce. Emma: Chris: In front of each gamete genotype above write probability of producing that gamete. c. What is the probability that Chris and Emma will have a child affected with SCA? (affected=has the disease="aa" =homozygous recessive) d. Write the cross and the Punnett square that demonstrates this. e. The phenotypic ratio is The genotypic ratio is normal : affected AA: Aa : aa 2. Chris and Emma are also carriers for CF (gene B is on chromosome 7). Both are genotype Bb. a. What is the probability that they will have a child affected with CF? (affected = has the disease = "bb" =homozygous recessive) b. Write the cross and the Punnett square that demonstrates this.
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