Discuss how Mendel's monohybrid results served as the basis for all but one of his postulates. Which postulate was not based on these results? Why?

Short Answer

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Answer: The postulate that was not based on Mendel's monohybrid results is the Law of Independent Assortment. This is because it concerns the inheritance of genes for two or more traits, rather than the inheritance of just one trait as observed in the monohybrid experiments. Mendel derived this postulate from his dihybrid cross experiments, where he studied the inheritance patterns of two traits and concluded that the genes for different traits were inherited independently of each other.

Step by step solution

01

Understand Mendel's Monohybrid Results

Gregor Mendel performed a series of experiments on pea plants to understand how traits are passed on from one generation to the next. In his monohybrid cross experiments, Mendel crossed pea plants that had contrasting traits for one characteristic, such as seed color (yellow or green). He then observed the traits in the resulting offspring and noticed a pattern in their inheritance.
02

Mendel's Postulates

Based on his monohybrid cross experiments, Mendel developed four postulates, which laid the foundation for the modern science of genetics. The postulates are as follows: 1. The Law of Segregation: Each organism has two alleles for a trait, and these alleles separate during the formation of gametes so that each gamete carries only one allele for a trait. 2. The Law of Dominance: In a pair of contrasting alleles, one allele is dominant, and the other is recessive. The dominant allele determines the organism's appearance, while the recessive allele has no effect on the organism's appearance. 3. The Law of Independent Assortment: Genes for different traits are inherited independently of each other during the formation of gametes. 4. The Law of Unit Characteristics: Each trait is determined by a pair of genes; one gene comes from the mother and one from the father.
03

Identify the postulate not based on monohybrid results

Based on our understanding of Mendel's monohybrid results and his postulates, we can determine that the third postulate, the Law of Independent Assortment, was not based on these results.
04

Explain why this postulate was not based on monohybrid results

The Law of Independent Assortment was not based on monohybrid results because it concerns the inheritance of genes for two or more traits, rather than inheritance of just one trait as observed in the monohybrid experiments. Mendel derived this postulate from another set of experiments, known as dihybrid crosses, in which he crossed pea plants that had contrasting traits for two characteristics, such as seed color and seed shape. By studying the inheritance patterns of these two traits, Mendel concluded that the genes for different traits were inherited independently of each other.

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Most popular questions from this chapter

Dentinogenesis imperfecta is a tooth disorder involving the production of dentin sialophosphoprotein, a bone-like component of the protective middle layer of teeth. The trait is inherited as an autosomal dominant allele located on chromosome 4 in humans and occurs in about 1 in 6000 to 8000 people. Assume that a man with dentinogenesis imperfecta, whose father had the disease but whose mother had normal teeth, married a woman with normal teeth. They have six children. What is the probability that their first child will be a male with dentinogenesis imperfecta? What is the probability that three of their six chil- dren will have the disease?

Two true-breeding pea plants were crossed. One parent is round, terminal, violet, constricted, while the other expresses the respective contrasting phenotypes of wrinkled, axial, white, full. The four pairs of contrasting traits are controlled by four genes, each located on a separate chromosome. In the \(\mathrm{F}_{1}\) only round, axial, violet, and full were expressed. In the \(\mathrm{F}_{2},\) all possible combinations of these traits were expressed in ratios consistent with Mendelian inheritance. (a) What conclusion about the inheritance of the traits can be drawn based on the \(\mathrm{F}_{1}\) results? (b) In the \(\mathrm{F}_{2}\) results, which phenotype appeared most frequently? Write a mathematical expression that predicts the probability of occurrence of this phenotype. (c) Which \(\mathrm{F}_{2}\) phenotype is expected to occur least frequently? Write a mathematical expression that predicts this probability. (d) In the \(F_{2}\) generation, how often is either of the \(P_{1}\) phenotypes likely to occur? (e) If the \(F_{1}\) plants were testcrossed, how many different phenotypes would be produced? How does this number compare with the number of different phenotypes in the \(\mathrm{F}_{2}\) generation just discussed?

A certain type of congenital deafness in humans is caused by a rare autosomal (not X-linked) dominant gene. (a) In a mating involving a deaf man and a deaf woman (both heterozygous), would you expect all the children to be deaf? Explain your answer. (b) In a mating involving a deaf man and a deaf woman (both heterozygous), could all the children have normal hearing? Explain your answer. (c) Another form of deafness is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal hearing? Explain your answer.

Two organisms, \(A A B B C C D D E E\) and aabbccddee, are mated to produce an \(\mathrm{F}_{1}\) that is self-fertilized. If the capital letters represent dominant, independently assorting alleles: (a) How many different genotypes will occur in the \(\mathrm{F}_{2}\) ? (b) What proportion of the \(\mathrm{F}_{2}\) genotypes will be recessive for all five loci? (c) Would you change your answers to (a) and/or (b) if the initial cross occurred between \(A A b b C C\)ddee\(\times\)aaBBccDDEE parents? (d) Would you change your answers to (a) and/or (b) if the initial cross occurred between \(A A B B C C D D E E \times\) aabbccddEE parents?

Tay-Sachs disease (TSD) is an inborn error of metabolism that results in death, often by the age of \(2 .\) You are a genetic counselor interviewing a phenotypically normal couple who tell you the male had a female first cousin (on his father's side) who died from TSD and the female had a maternal uncle with TSD. There are no other known cases in either of the families, and none of the matings have been between related individuals. Assume that this trait is very rare. (a) Draw a pedigree of the families of this couple, showing the relevant individuals. (b) Calculate the probability that both the male and female are carriers for TSD. (c) What is the probability that neither of them is a carrier? (d) What is the probability that one of them is a carrier and the other is not? [Hint: The \(p\) values in (b), (c), and (d) should equal \(1 .]\)

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