Concept explainers
Still referring to Problem 1, what will be the possible genotypes of offspring from the following matings? With what frequency will each genotype show up?
- a. AABB × aaBB
- b. AaBB × AABb
- c. AaBb × aabb
- d. AaBb × AaBb
a.
To predict: The predicted genotype frequencies among the offspring for the mating AABB × aaBB.
Introduction: The law of independent assortment and law of segregation are the laws proposed by Gregor Johann Mendel, a geneticist. Mendel proposed the law of independent assortment based on the results of monohybrid cross that “two alleles at any locus tend to separate from each other during meiosis, so they end up in different gametes”. Mendel proposed the law of independent assortment based on the results of dihybrid cross that “alleles at one locus tend to assort into gametes independently of alleles at other loci”. The number of possible allele combination for the given genotype is given by the formula 2n where “n” is the number of heterozygous alleles that are present.
Explanation of Solution
A monohybrid cross is constructed with Punnett square for the parents having the genotype AABB and aaBB.
All the offspring have the same genotype AaBB. Therefore, there is no genotype frequency.
b.
To predict: The predicted genotype frequencies among the offspring for the mating AaBB × AABb.
Introduction: The law of independent assortment and law of segregation are the laws proposed by Gregor Johann Mendel, a geneticist. Mendel proposed the law of independent assortment based on the results of monohybrid cross that “two alleles at any locus tend to separate from each other during meiosis, so they end up in different gametes”. Mendel proposed the law of independent assortment based on the results of dihybrid cross that “alleles at one locus tend to assort into gametes independently of alleles at other loci”. The number of possible allele combination for the given genotype is given by the formula 2n where “n” is the number of heterozygous alleles that are present.
Explanation of Solution
A monohybrid cross is constructed with Punnett square for the parents having the genotype AaBB and AABb.
The following is the frequency of genotypes.
Total number of possible genotypes = 4.
AABB=
AABb=
AaBB=
AaBb =
The frequency of all four genotypes is 25%.
c.
To predict: The predicted genotype frequencies among the offspring for the mating AaBb × aabb.
Introduction: The law of independent assortment and law of segregation are the laws proposed by Gregor Johann Mendel, a geneticist. Mendel proposed the law of independent assortment based on the results of monohybrid cross that “two alleles at any locus tend to separate from each other during meiosis, so they end up in different gametes”. Mendel proposed the law of independent assortment based on the results of dihybrid cross that “alleles at one locus tend to assort into gametes independently of alleles at other loci”. The number of possible allele combination for the given genotype is given by the formula 2n where “n” is the number of heterozygous alleles that are present.
Explanation of Solution
A monohybrid cross is constructed with Punnett square for the parents having the genotype AaBb and aabb
The following is the frequency of genotypes.
Total number of possible genotypes = 4.
AABB=
aaBB=
Aabb=
aabb =
The frequency of all four genotypes is 25%.
d.
To predict: The predicted genotype frequencies among the offspring for the mating AaBb × AaBb.
Introduction: The law of independent assortment and law of segregation are the laws proposed by Gregor Johann Mendel, a geneticist. Mendel proposed the law of independent assortment based on the results of monohybrid cross that “two alleles at any locus tend to separate from each other during meiosis, so they end up in different gametes”. Mendel proposed the law of independent assortment based on the results of dihybrid cross that “alleles at one locus tend to assort into gametes independently of alleles at other loci”. The number of possible allele combination for the given genotype is given by the formula 2n where “n” is the number of heterozygous alleles that are present.
Explanation of Solution
A monohybrid cross is constructed with Punnett square for the parents having the genotype AaBb and AaBb.
The following is the frequency of genotypes.
Total number of possible genotypes = 16.
AABB=
AABb=
AaBB=
AaBb=
AAbb=
Aabb=
aaBB=
aaBb=
aabb=
The frequency of genotypes AABB, aaBB , AAbb and aabb is 6.25%.
The frequency of genotypes AaBB, AABb, aaBb and Aabb is 12.5%.
The frequency of genotypes AaBb is 25%.
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Chapter 19 Solutions
EBK HUMAN BIOLOGY
- A. Select and assign symbols for the genes involved, and determine the genotypes of the parents and offspring in each cross. Pigeons may exhibit a checkered or plain color pattern. In a series of controlled matings, the following data were obtained. F1 Progeny P1 Cross Checkered Plain 1. (a) checkered x checkered 36 0 2. (b) checkered x plain 38 0 3. (c) plain x plain 0 35 Then F1 offspring were selectively mated with the following results. (The P1 cross giving rise to each F1 pigeon is indicated in parentheses.) F2 Progeny F1 x F1 Cross Checkered Plain 4. checkered (a) x plain (c) 34 0 5. checkered (b) x plain (c) 17 14 6. checkered (b) x checkered (b) 28 9 7. checkered (a) x checkered (b) 39 0arrow_forwardRead in your textbook about positive assortative mating. In this example, from your text, positive assortative mating is 100% (i.e. there is no random mating). Note that the frequency of heterozygotes is cut in half each generation. Does this match your answers above? Look at the actual values make sure you understand why positive assortative mating leads to an increase in homozygosity. (a) Only heterozygotes produce heterozygote offspring, but only 50% of the time Homozygote parent for A, Heterozygote parent Homozygote parent for A, Eggs A, A, Eggs A2 A, Eggs A2 A2 A, A, A, A, A, A, A, A, A, A2 A2 A2 A2 A2 A2 A, A, A, A, A, A, A, A2 A2 A2 A2 A2 Az A2 A2 (b) Effect of extreme inbreeding (self- fertilization) over time A, A, Homozygote A, A2 Heterozygote A2 A2 Homozygote The arrows represent A, p= 0.5 offspring genotypes that are produced by each parental genotype Generation 1 Az q = 0.5 100% 25% 50% 25% 100% A, p= 0.5 Az q= 0.5 Generation 2 100% 25% 50% 25% 100% The frequencies of…arrow_forwardExcessive secretion of male sex hormones results in premature sexual maturation in males and masculization of the sex characters in females. This disorder is called the adrenogenital syndrome, and in Switzerland there is an autosomal recessive form of the disease that affects about one in 5000 newborns. a. Assuming random mating, what is the allele frequency of the recessive? b. What is the frequency of heterozygous carriers?arrow_forward
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- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning